Substrate processing method and substrate processing apparatus

ABSTRACT

A substrate processing method includes (a) forming a recess on a workpiece by partially etching the workpiece; and (b) forming a film having a thickness that differs along a depth direction of the recess, on a side wall of the recess. Step (b) includes (b-1) supplying a first reactant, and causing the first reactant to be adsorbed to the side wall of the recess; and (b-2) supplying a second reactant, and causing the second reactant to react with the first reactant thereby forming a film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/804,807, filed on Feb. 28, 2020, which claimsfrom Japanese Patent Application Nos. 2019-036708 filed on Feb. 28,2019, 2019-203918 filed on Nov. 11, 2019, and 2020-024686 filed on Feb.17, 2020, the disclosures of which are incorporated herein in theirentirety by reference, and priority is claimed to each of the foregoing.

TECHNICAL FIELD

The present disclosure relates to a substrate processing method and asubstrate processing apparatus.

BACKGROUND

As the integration of a semiconductor device is progressed not only inthe horizontal direction but also in the vertical direction, an aspectratio of a pattern formed in a process of manufacturing semiconductordevices is also increasing. For example, in manufacturing a 3D NAND,channel holes are formed in a direction that penetrates a large numberof metal wiring layers. When 64 layers of memory cells are formed, theaspect ratio of the channel holes is as high as 45.

There have been various methods for precisely forming a pattern with ahigh aspect ratio. For example, there has been proposed a method ofrepeating an etching and a film formation on an opening formed of adielectric material in a substrate, thereby suppressing lateral etching(U.S. Patent Application Publication No. 2016/0343580). Further, therehas been proposed a method of combining an etching and a film formationwith each other, to form a protective film for preventing a lateraletching of a dielectric layer (U.S. Patent Application Publication No.2018/0174858).

SUMMARY

According to an aspect of the present disclosure, a substrate processingmethod which is implemented by a substrate processing apparatus includessteps (a) and (b). Step (a) forms a recess on a workpiece by partiallyetching the workpiece. Step (b) forms a film having a thickness thatdiffers along a depth direction of the recess. Step (b) includes steps(b-1) and (b-2). Step (b-1) supplies a first reactant, and causes thefirst reactant to be adsorbed to a side wall of the recess. Step (b-2)supplies a second reactant, and causes the second reactant to react withthe first reactant thereby forming a film.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating an example of flow of a substrateprocessing method according to a first embodiment.

FIGS. 2A to 2D are views for explaining an example of a pattern formedby the substrate processing method according to the first embodiment.

FIGS. 3A to 3D are views for explaining a suppression of shapeabnormality of a semiconductor pattern by the substrate processingmethod according to the first embodiment.

FIGS. 4A to 4D are views for explaining a first example of the substrateprocessing method according to the first embodiment.

FIGS. 5A to 5C are views for explaining a second example of thesubstrate processing method according to the first embodiment.

FIG. 6 is a view for explaining a control of coverage of a protectivefilm formed by the substrate processing method according to the firstembodiment.

FIGS. 7A and 7B are views for explaining a film thickness of theprotective film formed by the substrate processing method according tothe first embodiment.

FIG. 8 is a view for explaining a relationship between the filmthickness of the protective film formed by the substrate processingmethod according to the first embodiment and a pressure in a processingchamber.

FIG. 9 is a view for explaining an improvement of an etching rate whenthe substrate processing method according to the first embodiment isused.

FIG. 10 is a flowchart illustrating an example of flow of a substrateprocessing method according to a second embodiment.

FIGS. 11A to 11E are views illustrating an example of a pattern formedby the substrate processing method according to the second embodiment.

FIGS. 12A and 12B are views (first part) for explaining a suppression ofclosing of an opening by the substrate processing method according tothe second embodiment.

FIGS. 13A to 13E are views (second part) for explaining a suppression ofclosing of an opening by the substrate processing method according tothe second embodiment.

FIGS. 14A to 14E are views for explaining a substrate processing methodaccording to a third embodiment.

FIG. 15 is a flowchart illustrating an example of flow of the substrateprocessing method according to the third embodiment

FIG. 16 is a flowchart illustrating an example of flow of a substrateprocessing method according to Modification 1.

FIGS. 17A to 17D are views for explaining an example of a workpieceprocessed by the substrate processing method according to Modification1.

FIG. 18 is a flowchart illustrating an example of a flow of a substrateprocessing method according to a fourth embodiment.

FIGS. 19A to 19D are views illustrating an example of a workpieceprocessed by the substrate processing method according to the fourthembodiment.

FIGS. 20A to 20D are views illustrating another example of the workpieceprocessed by the substrate processing method according to the fourthembodiment.

FIGS. 21A and 21B are views for explaining a relationship between atemperature of a workpiece and a film formation amount.

FIGS. 22A to 22C are views for explaining an example of a workpieceprocessed by a substrate processing method according to Modification 3.

FIG. 23 is a view illustrating an example of a substrate processingapparatus according to the first embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawing, which form a part hereof. The illustrativeembodiments described in the detailed description, drawing, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

Hereinafter, embodiments of the present disclosure will be described indetail based on the drawings. In addition, the embodiments do not limitthe present disclosure. Further, the embodiments may be appropriatelycombined with each other within a range that does not cause anyinconsistency in processing contents. Further, in the respectivedrawings, the same or corresponding portions will be denoted by the samereference numerals.

It is known that a shape abnormality occurs when a pattern with a highaspect ratio is etched. For example, when an opening is formed in thevertical direction, there occurs a shape abnormality that the innerperipheral surface of the opening expands in the horizontal direction.This shape abnormality is called bowing. There has been proposed amethod of forming a protective film on the side wall of an opening inorder to suppress the occurrence of shape abnormality. In forming a finepattern, it is preferable to prevent a closing of the opening due to theprotective film or a decrease in etching rate due to a film formation onthe bottom of the opening.

In the following description, a “pattern” refers to all shapes formed ona substrate. A pattern indicates all of a plurality of shapes formed ona substrate such as, for example, holes, trenches, and line-and-space.In addition, a “recess” refers to a portion corresponding to a shapedented in a thickness direction of a substrate in a pattern formed onthe substrate. Further, the recess has a “side wall” which is the innerperipheral surface of the dented shape, a “bottom” which is the bottomof the dented shape, and a “top” which is continuous with the side walland is the surface of the substrate near the side wall. In addition, thespace surrounded by the top is called an “opening.” Further, the term“opening” is also used to indicate the entire space surrounded by thebottom and the side wall of the recess or an arbitrary position in thespace.

Example of Flow of Substrate Processing Method according to FirstEmbodiment

FIG. 1 is a flowchart illustrating an example of flow of the substrateprocessing method according to a first embodiment. First, a workpiece isprovided (step S100). For example, a substrate on which a pattern with ahigh aspect ratio is formed is disposed in a processing chamber.Alternatively, for example, a substrate on which no pattern is formed isdisposed in the processing chamber, and partially etched to form apattern (step (a)). Next, a first gas (hereinafter, also referred to asa precursor or a first reactant) is introduced into the processingchamber (step S101, a first step, or step (b-1)). Next, the processingchamber is purged to discharge the component of the first gas that isexcessively adsorbed onto the surface of the workpiece (step S102).Next, a second gas (hereinafter, also referred to as a reaction gas or asecond reactant) is introduced into the processing chamber (step S103, asecond step, or step (b-2)). Then, the processing chamber is purged todischarge the excessive component of the second gas (step S104). Inaddition, steps S100 and S101 to S104 may be performed in the sameprocessing chamber (in-situ) or in different processing chambers(ex-situ). Next, it is determined whether a protective film formed onthe workpiece in steps S101 to S104 reaches a predetermined filmthickness (step S105). The determination of whether the protective filmreaches the predetermined film thickness may be performed based on thenumber of times of performing steps S101 to S104. Alternatively, thedetermination may be performed based on a measured value of the filmthickness of the protective film. The measured value may include aparameter that indicates a state of the protective film such as adistribution of the film thickness. The method of measuring theprotective film is not particularly limited, and the protective film maybe measured by, for example, an optical method. For in-situ, the filmthickness may be measured using a measurement apparatus provided inadvance in the processing chamber. Meanwhile, for ex-situ, the filmthickness may be measured using a measurement apparatus provided outsidethe processing chambers. As a result, when it is determined that theprotective film does not reach the predetermined film thickness (stepS105, No), the process returns to step S101 to repeat steps S101 toS104. In this case, the processing conditions in steps S101 to S104 maybe adjusted according to the measured value. Meanwhile, when it isdetermined that the protective film reaches the predetermined filmthickness (step S105, Yes), the workpiece is etched (step S106). At thistime, the etching condition may be adjusted according to the measuredvalue that is obtained in step S105. Then, it is determined whether theetched pattern has a predetermined shape (step S107). The determinationof whether the etched pattern has the predetermined shape may beperformed based on the number of times of performing step S106.Alternatively, the determination may be performed based on a measuredvalue of the shape of the etched pattern. The method of measuring theshape of the etched pattern is not particularly limited, and the shapeof the etched pattern may be measured by, for example, an opticalmethod. For in-situ, the shape of the etched pattern may be measuredusing a measurement apparatus provided in advance in the processingchamber. Meanwhile, for ex-situ, the shape of the etched pattern may bemeasured using a measurement apparatus provided outside the processingchambers. As a result, when it is determined that the etched patterndoes not have the predetermined shape (step S107, No), the processreturns to step S101 to repeat the first and second steps. Meanwhile,when it is determined that the etched pattern has the predeterminedshape (step S107, Yes), the process is ended. This flow is an example ofthe process flow of the substrate processing method according to thefirst embodiment.

In the process illustrated in FIG. 1 , the processing conditions in thefirst and second steps are set such that the coverage of the protectivefilm by at least one of the first and second gases along the depthdirection of the pattern changes. The coverage refers to an area ratioof a protective film formed to have a predetermined film thickness perunit area. That is, the processing conditions are set such that the filmthickness of the protective film formed in the first and second stepschanges in the depth direction of the pattern. In addition, the purgingin steps S102 and S104 may be omitted.

In addition, the determination in step S105 is performed based on, forexample, whether steps S101 to S104 have been performed a predeterminednumber of times. Further, the determination in step S107 is performedbased on, for example, whether step S106 has been performed on the sameworkpiece a predetermined number of times. In addition, the etching instep S106 may be performed a plurality of times.

In addition, steps S101 and S103 may be performed using plasma or may beperformed without using plasma. In addition, the respective steps may beperformed in the same processing chamber while maintaining adepressurized atmosphere, or may be performed in different processingchambers. In addition, when the steps are performed in differentprocessing chambers, the steps may be performed while maintaining thedepressurized atmosphere or may be performed passing through a normalpressure atmosphere.

FIGS. 2A to 2D are views for explaining an example of a pattern formedby the substrate processing method according to the first embodiment.The substrate processing method of the first embodiment will be furtherdescribed with reference to FIGS. 2A to 2D.

A workpiece S illustrated in FIGS. 2A to 2D includes an etching targetfilm 102 and a mask 120 which are stacked on a substrate 101. First, theworkpiece S is disposed in the processing chamber. Next, in step S101,the first gas is introduced into the processing chamber. The first gasis adsorbed to a top 200T, a side wall 200S, and a bottom 200B thatsurrounds an opening 200, so as to form the layer illustrated in FIG.2A. After the processing chamber is purged, the second gas is introducedinto the processing chamber in step S103 (FIG. 2B). The processingconditions in steps S101 and S103 are set such that the reaction betweenthe component of the second gas and the component of the first gasadsorbed onto the workpiece S is not completed on the entire surfacelayer of the workpiece S. After a processing time based on the setprocessing conditions elapses, the processing chamber is purged. Thesecond gas reacts with the first gas on the top 200T and the upperportion of the side wall 200S, thereby forming a protective film 300(FIG. 2C). Thereafter, steps S101 to S104 are repeated such that aprotective film 301 having a desired film thickness is formed (FIG. 2D).Then, in step S106, the etching target film 102 is etched. Since theprotective film 301 is formed in advance at the portion where the shapeabnormality occurs due to the etching, the occurrence of shapeabnormality after the etching is prevented.

Suppression of Shape Abnormality

FIGS. 3A to 3D are views for explaining the suppression of shapeabnormality of a semiconductor pattern by the substrate processingmethod according to the first embodiment. The workpiece S illustrated inFIG. 3A is the same as the workpiece S illustrated in FIG. 2D, and theprotective film 301 is formed on the top 200T and the side wall 200S. Inthe etching, bowing often occurs at a position where the mask isswitched to the etching target film. For example, bowing often occurs atthe position R1 indicated in FIG. 3A. However, in the example of FIGS.3A to 3D, the protective film 301 is formed at the position R1 to becomethinner in the depth direction of the pattern. Accordingly, after theworkpiece S is etched, the protective film 301 is shaved much at theposition R1, so that an opening dimension in the depth direction becomesuniform, as illustrated in FIG. 3B. As the etching is repeated, theprotective film 301 is further shaved, so that the opening dimensionbecomes substantially uniform from the upper portion toward the lowerportion of the opening 200 as illustrated in FIG. 3C, and for example,becomes the shape illustrated in FIG. 3D. When bowing of the protectivefilm 301 occurs due to the etching (corresponding to No in step S107),the first and second steps are performed again to form the protectivefilm 301 again. In this way, according to the substrate processingmethod according to the first embodiment, the shape abnormality of asemiconductor pattern may be suppressed.

ALD Control for Changing Film Thickness in Depth Direction of Pattern

As described above, in the substrate processing method according to thefirst embodiment, the protective film of which coverage (film thickness)decreases in the depth direction is formed on the inner peripheralsurface of the opening. As for a method of forming the protective film,for example, a chemical vapor deposition or an atomic layer deposition(ALD) may be used. The substrate processing method according to thefirst embodiment forms the protective film having a film thickness thatdiffers in the depth direction of the opening, while changing thecoverage in the depth direction of the opening by using aself-controllability of a film formed by the ALD.

Prior to describing the substrate processing method according to thefirst embodiment, the so-called ALD will be described. The ALD typicallyincludes four processing steps. First, the first gas (also referred toas a precursor) is introduced into a processing chamber in which aworkpiece, for example, a substrate is disposed. A first materialincluded in the first gas is adsorbed on the surface of the workpiece.After the surface of the workpiece is covered with the first material,the processing chamber is evacuated. Next, the second gas that includesa second material reacting with the first material (also referred to asa reaction gas) is introduced into the processing chamber. The secondmaterial reacts with the first material on the workpiece, therebyforming a film. When the reaction with the first material on the surfaceis completed, the film formation is ended. The ALD forms a film bycausing a predetermined material to be adsorbed to and react with amaterial existing in advance on the surface of the workpiece in aself-controlled manner. Thus, the ALD typically implements a conformalfilm formation by providing a sufficient processing time.

Meanwhile, the substrate processing method according to the firstembodiment sets the processing conditions such that the self-controlledadsorption or reaction on the surface of the workpiece is not completed.At least two processing aspects are provided below.

(1) The precursor is adsorbed to the entire surface of the workpiece. Acontrol is performed to suppress the reaction gas introduced thereafterfrom spreading over the entire surface of the workpiece evenly.

(2) The precursor is adsorbed to only a portion of the surface of theworkpiece. The reaction gas introduced thereafter forms a film only onthe portion of the surface to which the precursor is adsorbed.

The substrate processing method according to the first embodiment usesthe method (1) or (2), to suppress the protective film from being formedon the lower portion of the side wall of the opening and the bottom ofthe opening in the semiconductor pattern.

FIGS. 4A to 4D are views for explaining a first example of the substrateprocessing method according to the first embodiment. The workpieceillustrated in FIGS. 4A to 4D includes an etching target film EL1 and amask MA which are formed on a substrate (not illustrated). A recesshaving an opening OP is formed in the stacked body of the etching targetfilm EL1 and the mask MA.

First, a precursor P is introduced into the processing chamber in whichthe workpiece is disposed (FIG. 4A). By providing a sufficientprocessing time for the adsorption of the precursor P, the precursor Pis adsorbed to the entire surface of the workpiece (FIG. 4B). When theadsorption of the precursor P is completed, the processing chamber ispurged. Next, a reaction gas R is introduced into the processing chamber(FIG. 4C). The introduced reaction gas R reacts with the precursor P onthe workpiece, thereby forming a protective film PF gradually from thetop of the mask MA. Here, the reaction gas R is purged before theprotective film PF being formed reaches the lower portion of the etchingtarget film EL1 With this processing, it is possible to form theprotective film PF only on the mask MA and the upper portion of theetching target film EL1 rather than on the entire side wall of therecess, using the ALD method (FIG. 4D). In FIG. 4D, the protective filmPF is formed on the upper portion of the side wall of the recess and thetop of the recess, and is not formed on the lower portion of the sidewall of the recess and the bottom of the recess.

FIGS. 5A to 5C are views for explaining a second example of thesubstrate processing method according to the first embodiment. Theworkpiece illustrated in FIGS. 5A to 5C has the same shape as that ofthe workpiece of FIGS. 4A to 4D.

In the example of FIGS. 5A to 5C, the precursor P is adsorbed only tothe upper portion of the workpiece (FIG. 5A). After the precursor P ispurged, the reaction gas R is introduced into the processing chamber(FIG. 5B). At this time, since the reaction gas R reacts with theprecursor P and forms a film only on the position to which the precursorP is adsorbed, the protective film PF is formed only on the upperportion of the workpiece (FIG. 5C).

Processing Conditions for Selective Adsorption and Reaction

As described above, in the substrate processing method according to thefirst embodiment, the adsorption of the precursor in the second exampleor the reaction of the reaction gas in the first example occurs at apredetermined portion of the pattern. For example, since the protectivefilm is formed only on the upper portion of the opening of the pattern,the processing conditions are adjusted such that the adsorption of theprecursor or the reaction of the reaction gas occurs only at the upperportion of the opening of the pattern.

The processing parameters to be adjusted for implementing the substrateprocessing method are, for example, the temperature of the stage onwhich the workpiece is disposed, the pressure in the processing chamber,the flow rate and the introduction time of the precursor to beintroduced, and the gas flow rate and the introduction time of thereaction gas to be introduced, and the processing time. In addition,when a processing is performed using plasma, the position of the filmformation may also be adjusted by adjusting a value of a radio-frequency(RF) power applied for generating plasma.

FIG. 6 is a view for explaining a control of the coverage of theprotective film formed by the substrate processing method according tothe first embodiment. In FIG. 6, the horizontal axis represents theprocessing time, and the vertical axis represents the coverage. Further,the solid line represents the coverage at the top TOP of the recess ofthe pattern, the alternate long and short dash line represents thecoverage at the center MIDDLE of the side wall of the recess, and thedashed line represents the coverage at the bottom BOTTOM of the recess.Further, FIG. 6 represents an approximate tendency, rather than exactnumerical values.

As illustrated in FIG. 6 , when the film formation is performed in therecess of the pattern, the rate of the film formation (adsorption orreaction) differs at each of the top, the center of the side wall, andthe bottom of the recess. The film formation is progressed graduallyfrom the top to which the precursor or the reaction gas is initiallyintroduced, toward the bottom. First, as represented by the solid linein FIG. 6 , the coverage at the top gradually increases, and the filmformation on the top is completed earliest among the film formations atthe portions of the recess (timing T₁, coverage 100%). Next, asrepresented by the alternate long and short dash line, the filmformation on the center of the side wall is progressed in a slightlyslower rate than that on the top, and completed at a timing T₂ which isslightly later than the timing at which the film formation on the top iscompleted. Next, as represented by the dashed line, the film formationon the bottom is progressed, and completed at a timing T₃ which is thelatest among the timings for the portions of the recess.

Accordingly, when the adsorption of the precursor or the reaction of thereaction gas is ended at a timing after the timing T₁ and before thetiming T₃, the processing may be ended in a state where the precursor isadsorbed to or the protective film is formed on the top of the recess,but the adsorption of the precursor or the formation of the protectivefilm to/on the center of the side wall or the bottom is not completed.

In FIG. 6 , the coverage is plotted by setting the processing time as aprocessing parameter on the horizontal axis. Alternatively, the coveragemay also be adjusted by fixing the processing time, and changing thetemperature of the stage, the pressure in the processing chamber, thegas flow rate (dilution degree) of the precursor or the reaction gas, oran absolute value of the radio-frequency (RF) power applied forgenerating plasma. For example, by setting the temperature of the stageto be low, the progress of the film formation on the lower portion ofthe pattern may be made slow. In addition, by setting the pressure inthe processing chamber to be low, the progress of the film formation onthe lower portion of the pattern may be made slow. In addition, bysetting the flow rate of the precursor included in a gas to beintroduced to be low, the progress of the adsorption to the lowerportion of the pattern may also be made slow. In addition, by settingthe flow rate of the reaction gas to be introduced to be low, theprogress of the film formation on the lower portion of the pattern mayalso be made slow. In addition, when plasma is used, the progress of thefilm formation on the lower portion of the pattern may be made slow, bysetting an absolute value of the radio-frequency power applied forgenerating plasma to be low.

For example, each of the temperature of the stage, the pressure in theprocessing chamber, the dilution degree of the gas to be introduced(precursor), and the absolute value of the radio-frequency power is setto a smaller value than a value at which the adsorption of the precursorto the entire surface of the workpiece is completed, when the otherprocessing conditions are the same. In addition, for example, each ofthe temperature of the stage, the pressure in the processing chamber,and the absolute value of the radio-frequency power is set to a smallervalue than a value at which the reaction of the reaction gas on theentire surface of the workpiece is completed, when the other processingconditions are the same. In addition, the dilution degree of the gas tobe introduced (reaction gas) is set to a higher value than the value atwhich the reaction of the reaction gas on the entire surface of theworkpiece is completed, when the other processing conditions are thesame.

In the substrate processing method according to the first embodiment,the processing conditions are adjusted as described above, such that theprocessing is ended in a state where the adsorption of the precursorrepresented in the second example or the reaction of the reaction gasrepresented in the first example is unsaturated. As a result, theprotective film may be formed only on the upper portion of the patternby the substrate processing method according to the first embodiment.

Film Thickness of Protective Film Formed by Substrate Processing Methodaccording to First Embodiment

FIGS. 7A and 7B are views for explaining the film thickness of theprotective film formed by the substrate processing method according tothe first embodiment. As described above, in the first embodiment, theprocessing conditions are adjusted such that the protective film isformed on the upper portion of the pattern. The inventors of the presentdisclosure processed a workpiece using the substrate processing methodaccording to the first embodiment, and examined the film thickness ofthe formed protective film. FIG. 7A is a schematic view of the workpieceused in the experiment. The workpiece includes the etching target filmEL1, the mask MA formed on the etching target film EL1, and the recessformed in the mask MA and the etching target film EL1 and having theopening OP. FIG. 7A represents a state where the protective film PF isformed on the entire inner surface of the recess. The CD refers to ahorizontal dimension of the space surrounded by the side wall of therecess at an arbitrary position in the space.

FIG. 7B represents plots of an opening dimension in the initial state ofthe workpiece, an opening dimension after a processing according toExample 1 is performed, an opening dimension after a processingaccording to Reference Example 1 is performed, in association with thedepth of the opening in the etching target film EL1 The initial staterefers to a state before the protective film PF is formed. Example 1corresponds to a case where the protective film is formed on theworkpiece by the substrate processing method according to the firstembodiment. Specifically, the processing time for the reaction of thereaction gas is set to be short (see the timing T₂ in FIG. 6 ).Reference Example 1 corresponds to a case where the protective film isformed on the workpiece by the normal ALD. The normal ALD refers to anALD that implements the conformal film formation by providing asufficient time until each of the absorption of the precursor and thereaction of the reaction gas to/on the entire surface of the workpieceis completed.

As represented in FIG. 7B, first, in the initial state, the openingdimension is about 40 nanometers (nm) at the depth position of about 0.0micrometer (μm), and about 30 nm at the depth position of about 1.4 μm.That is, as the depth increases, the opening dimension decreases. Afterthe normal ALD is performed, the protective film is formed to have asubstantially constant film thickness, regardless of the depth. Theopening dimension at the depth position of about 0.0 μm is about 25 nm,and the opening dimension at the depth position of about 1.4 μm is about18 nm. While there is a slight error according to the depth, theprotective film of about 12 nm to 15 nm is formed. Meanwhile, after theprocessing by the substrate processing method according to the firstembodiment (Example 1) is performed, the opening dimension at the depthposition of about 0.0 μm is 30 nm, and the opening dimensions at thedepth positions of about 0.4 μm and about 1.3 μm are about 34 nm and 30nm, respectively. That is, the film thickness of the formed protectivefilm gradually decreases from the top toward the bottom of the recess.The film thickness of the protective film formed by the substrateprocessing method according to the first embodiment gradually changesfrom the upper portion toward the lower portion of the recess. That is,the substrate processing method according to the first embodiment formsthe protective film which is not conformal, that is, a sub-conformalprotective film, using the ALD method.

FIG. 8 is a view for explaining a relationship between the distributionof the film thickness of the protective film formed by the substrateprocessing method according to the first embodiment in the depthdirection and the pressure in the processing chamber. When theprocessing conditions other than the pressure are constant, a totaldeposition amount of the deposited film largely differs according to thepressure. Thus, the total deposition amount obtained by adding up thefilm thickness of the deposited film up to the depth of 1.5 μm isnormalized to 1, and a ratio of a deposition amount from the depth of 0μm to a predetermined depth is plotted to represent differences amongthe conditions. Reference Example 1 of FIG. 8 corresponds to a casewhere the protective film is formed on the workpiece by the normal ALD.In the normal ALD, since the conformal film formation is implemented,the film thickness is constant in the depth direction. Thus, a primarycurve is drawn in the graph of FIG. 8 . In addition, the other graphs ofFIG. 8 represent the distributions of the film thickness in a case whereamong the processing conditions of Example 1 in FIG. 7B, the pressure inthe processing chamber when the reaction of the reaction gas isconducted is changed to 200 mTorr (mT), 20 mT, and 10 mT. As representedin FIG. 8 , it may be seen that for any of the pressure values, thetotal deposition amount of the deposited film at the relatively shallowdepth position is larger than that in Reference Example 1. That is, thegraphs represent that the sub-conformal protective film is formed. Inparticular, it may be seen that the total deposition amount of thedeposited film at the relatively shallow depth position is large in acase where the pressure is 10 mT. In other words, in order to change thefilm thickness of the protective thickness according to the depth andincrease the film thickness toward the top, it is preferable to set thepressure in the processing chamber to be low.

In addition, the inventors of the present disclosure used oxygen gas(O₂) as the reaction gas and a substrate having a pattern with an aspectratio of about 10 as the workpiece, and examined the change of the filmthickness of the protective film according to the dilution degree of theoxygen gas, among the processing conditions of Example 1 in FIG. 7B,when the reaction of the reaction gas was conducted. The dilution degreeof the oxygen gas refers to a ratio of a diluting gas to the total flowrate of the oxygen gas and the diluting gas. The dilution degree of theoxygen gas may be represented by being replaced with a partial pressureof the diluting gas. In addition, the diluting gas refers to a gas thatdoes not contribute to a reaction and is composed of a non-reactant suchas a rare gas. O₂ was used as the reaction gas, argon gas was used asthe diluting gas, and a mixture of O₂ and argon gas at a predeterminedratio was used. As a result, the film thickness of the protective filmchanged according to the depth of the recess, and the change of the filmthickness increased as the dilution degree of O₂ was high. This isbelieved to be because it is easy for O radicals to spread sufficientlyand evenly over the bottom of the recess, and the amount of O radicalssupplied to the bottom is suppressed by increasing the dilution degree.

As described above, the substrate processing method according to thefirst embodiment forms the film having the self-controllability suchthat the film has the different coverage and film thickness along thedepth direction of the pattern, by using the ALD method and adjustingthe processing conditions.

Improvement of Etching Rate

FIG. 9 is a view for explaining an improvement of an etching rate by thesubstrate processing method according to the first embodiment. FIG. 9represents an experimental result obtained in a case where a mask MA ofa silicon oxynitride film is stacked on an amorphous carbon layer whichis the etching target film EL1 and the amorphous carbon layer is etchedusing a pattern formed on the mask.

The leftmost view (initial state) of FIG. 9 represents a state of theworkpiece at the start time of the processing. In the initial state, theopening dimension is slightly large near the top of the etching targetfilm EL1 and the opening has a shape tapered in the depth direction.

The second leftmost view of FIG. 9 (Reference Example 1) represents aresult obtained when the workpiece in the initial state is directlyetched. In Reference Example 1, the opening dimension is largelyexpanded below the mask, and bowing occurs (the portion “A1” in FIG. 9). The second rightmost view of FIG. 9 (Reference Example 2) representsa result obtained when etching is performed after a protective film isformed by the normal ALD. Upon a comparison with Reference Example 1,the occurrence of bowing in the etching target film immediately belowthe mask is suppressed (the portion “A2” in FIG. 9 ), but the depth ofthe recess formed by the etching is largely reduced. The rightmost viewof FIG. 9 (Example 1) represents a result obtained when etching isperformed after a protective film is formed using the substrateprocessing method according to the first embodiment. Upon a comparisonwith Reference Example 2, the suppression degree of the occurrence ofbowing is substantially the same (the portion “A3” in FIG. 9 ), but thedepth of the recess formed by etching largely increases.

When the protective film is formed by the normal ALD, the protectivefilm is formed not only on the side wall of the recess but also on thebottom of the recess. Accordingly, the protective film acts as anetching stop layer, and thus, the etching rate decreases. In themeantime, in the substrate processing method according to the firstembodiment, the film formation on the bottom of the recess issuppressed, and the protective film is formed on the side wall of therecess. Since the protective film is suppressed from being formed on thebottom of the recess and acting as an etching stop layer, the decreaseof the etching rate may be suppressed.

In addition, in the substrate processing method according to the firstembodiment, since the film formation on the side wall of the recess nearthe bottom of the recess is suppressed, the dimension of the bottom ofthe recess may be controlled. For example, in a case where a recess isformed to have a diameter that is reduced from the top toward thebottom, a control may be implemented to increase the dimension of thebottom while suppressing the change of the dimension of the side wall bythe protective film.

Further, in the substrate processing method according to the firstembodiment, since the film formation is performed using the ALD method,a fine control of the film thickness is possible. Thus, the opening isprevented from being closed at the top of the recess.

Film Type of Workpiece

In addition, the type of the etching target film 102 in the firstembodiment is not particularly limited. The etching target film 102 maybe, for example, a silicon-containing film, a carbon-containing film, anorganic film or a metal film. The silicon-containing film may be asilicon dielectric film, and examples of the silicon-containing filminclude a silicon oxide film, a silicon nitride film, a siliconoxynitride film, and silicon carbide.

In addition, the types of the protective films 300 and 301 formed by thesubstrate processing method according to the first embodiment may be thesame as the type of the etching target film 102. For example, each ofthe protective films 300 and 301 may be a silicon-containing film, acarbon-containing film, an organic film or a metal film. Thecarbon-containing film is, for example, an amorphous carbon layer (ACL)or a spin-on-carbon film. In addition, the silicon-containing dielectricfilm is, for example, a silicon oxide film (SiO), a silicon nitride film(SiN), a silicon oxynitride film (SiON) or a combination thereof Themetal film is, for example, a titanium (Ti) film or a tungsten (W) film.As described above, when the types of the protective films 300 and 301and the etching target film 102 are the same, it becomes easy to controla subsequent processing. For example, at the time of etching, theetching rates of the protective films 300 and 301 and the etching targetfilm 102 may become uniform. Thus, the dimension of the bottom 200B maybe easily controlled during the etching after the protective films 300and 301 are formed. For example, when the types of the protective films300 and 301 are different from the type of the etching target film 102,it may be considered that the protective films 300 and 301 are notremoved and remain in the subsequent etching step, and thus, the bottom200B of the etching target film 102 is excessively shaved. Meanwhile,when the types of the protective films 300 and 301 and the etchingtarget film 102 are the same, the amount removed by etching may beeasily controlled. In addition, when the protective films 300 and 301are removed in the subsequent processing, the protective films 300 and301 may be removed together with the etching target film 102 withoutproviding a separate step for removing the protective films 300 and 301.

In addition, the etching target film 102 may be a stacked film in whicha plurality of layers is stacked. For example, the etching target film102 may be an ONON film (silicon oxide film/silicon nitride film) or anOPOP film (silicon oxide film/polysilicon).

In addition, when a silicon oxide film is formed as each of theprotective films 300 and 301, an aminosilane-based gas, SiCl₄, SiF₄ orthe like may be used as the precursor, and an oxygen-containing gas suchas, for example, O₂ may be used as the reaction gas. In addition, when asilicon nitride film is formed as each of the protective films 300 and301, an aminosilane-based gas, SiCl₄, dichlorosilane (DCS),hexachlorodisilane (HCDS) or the like may be used as the precursor, anda nitrogen-containing gas such as, for example, N₂ or NH₃ may be used asthe reaction gas. In addition, as a method of forming an organic film aseach of the protective films 300 and 301, a molecular layer deposition(MLD) may be used. In addition, when a titanium film or a titanium oxidefilm is formed as each of the protective films 300 and 301, TDMAT(tetrakis(dimethylamino)titanium) or titanium tetrachloride (TiCl₄) maybe used as the precursor, and a reducing gas or an oxidizing gas may beused as the reaction gas. In addition, when a tungsten film is formed,WF₆ may be used as the precursor, and a reducing gas may be used as thereaction gas.

In addition, the precursor may be selected to control the depth of theprotective films 300 and 301 to be formed. For example, as for theselection of the precursor for forming the protective films 300 and 301only on the further upper portion of the pattern among aminosilane-basedgases, it is preferable to use aminosilane gas having two or three aminogroups (divalent or trivalent aminosilane), rather than aminosilane gashaving one amino group (monovalent aminosilane). In addition, in orderto form the protective films 300 and 301 at a deep position of thepattern, it is preferable to use monovalent aminosilane gas. Inaddition, by a combination with the processing parameters such as theprocessing time, the temperature of the stage, and the pressure in theprocessing chamber, the controllability of the unsaturated state may beimproved.

In addition, plasma may be generated during the supply of the precursorand the reaction gas. For example, the precursor and the reaction gasmay be dissociated by the plasma to generate radicals of the precursorhaving a relatively high adsorbability and radicals of the reaction gashaving a relatively high reactivity, so that the adsorption of theprecursor and the reaction of the reaction gas may be promoted. Inaddition, the plasma may not be necessarily generated as long as theprecursor and the reaction gas react with each other sufficiently andspontaneously.

In addition, the substrate processing method according to the firstembodiment is not limited to, for example, a 3D NAND or a DRAM, and maybe applied to the manufacture of a semiconductor device having a patternwith a high aspect ratio. For example, the substrate processing methodaccording to the first embodiment may be applied to a processing of anorganic film with a high aspect ratio which is used for a multilayerresist mask or the like. Here, the high aspect ratio means that theratio of the depth of the recess to the width of the recess is at least5 or 10 or more.

Second Embodiment—Control Using Inhibitor

FIG. 10 is a flowchart illustrating an example of flow of a substrateprocessing method according to a second embodiment. FIGS. 11A to 11E areviews illustrating an example of a pattern formed by the substrateprocessing method according to the second embodiment. In addition, theworkpiece illustrated in FIG. 11A is the same as the workpiece in FIG.2A. In the first embodiment, the sub-conformal film formation isimplemented by adjusting the adsorption position or the reactionposition of at least one of the first gas and the second gas. In thesecond embodiment, the adsorption position of the precursor iscontrolled by forming a factor for inhibiting the adsorption of theprecursor (hereinafter, also referred to as an inhibitor) in advance ona portion of the surface of the workpiece. For example, a factor forforming a hydrophobic group that inhibits the adsorption of theprecursor is formed on the upper portion of the workpiece by the CVD.

First, the workpiece is provided (step S200). For example, a substrateon which a pattern with a high aspect ratio is formed is disposed in theprocessing chamber, as in the first embodiment. Alternatively, forexample, a substrate on which no pattern is formed is disposed in theprocessing chamber, and partially etched to form a pattern. Next, a gascontaining an inhibitor for inhibiting the adsorption of the first gasis introduced into the processing chamber (step S201). The gascontaining the inhibitor is, for example, a gas containing carbon. Thegas containing carbon is, for example, fluorocarbon gas,fluorohydrocarbon gas or hydrocarbon gas. In FIG. 11A, when plasma CVDis performed using fluorocarbon gas, a fluorocarbon film is formed as aninhibitor layer IN. In addition, in FIG. 11A, when plasma CVD isperformed using fluorohydrocarbon gas, a fluorohydrocarbon film isformed as an inhibitor layer IN. In addition, in FIG. 11A, when plasmaCVD is performed using hydrocarbon gas, a hydrocarbon film is formed asan inhibitor layer IN. The fluorocarbon film, the fluorohydrocarbonfilm, and the hydrocarbon film are hydrophobic films. Here, theprocessing conditions of the plasma CVD are adjusted to form theinhibitor layer IN as illustrated in FIG. 11B. In the example of FIG.11B, the inhibitor layer IN is formed on the top 200T and the bottom200B.

Next, as illustrated in FIG. 11C, the first gas (the precursor P, thefirst reactant) is introduced into the processing chamber (step S202,the first step). The precursor P is not absorbed to the portions onwhich the inhibitor layer IN is formed. Thus, the precursor P isselectively adsorbed to the side wall 200S (see FIG. 11D). After theprocessing chamber is purged (step S203), the second gas (the reactiongas R, the second reactant) is introduced into the processing chamber(step S204, the second step, FIG. 11E). The reaction gas R reacts withthe atoms of the precursor P only at the position to which the precursorP is adsorbed, so as to form a protective film 302. Thus, as illustratedin FIG. 11E, the protective film 302 is formed only on the side wall200S. Further, the processing chamber is purged (step S205). Steps S206to S208 are the same as steps S105 to S107 in FIG. 1 .

In the second embodiment, for example, an aminosilane-based gas, asilicon-containing gas, a titanium-containing gas, a hafnium-containinggas, a tantalum-containing gas, a zirconium-containing gas or anorganic-containing gas may be used as the precursor P. The precursor Pis adsorbed only to the region on which the inhibitor layer IN is notformed, so as to form a precursor layer. In addition, when the precursorP is adsorbed, plasma may or may not be generated.

After the precursor P is introduced and before the reaction gas R isintroduced, the purging step is performed using an inert gas such asargon or nitrogen gas, to reduce or remove the precursor P remaining inthe processing chamber, mainly in the gas phase. In addition, thepurging step may be performed by evacuating the inside of the processingchamber. The excessively adsorbed precursor P is removed by the purging,and the precursor layer becomes substantially a monolayer.

In addition, the reaction gas R is, for example, an oxygen-containinggas, a nitrogen-containing gas or a hydrogen-containing gas. Thereaction gas R may include, for example, any of O₂ gas, CO₂ gas, NO gas,SO₂ gas, N₂ gas, H₂ gas, and NH₃ gas. The precursor layer is modified bythe reaction gas R so that the protective film 302 is formed, andsimultaneously, the surface of the inhibitor layer IN is removed so thatthe film thickness of the inhibitor layer IN is reduced or removed.

After the protective film 302 is formed, the purging step is performedusing an inert gas such as argon or nitrogen gas to reduce or dissipatethe reaction gas R remaining in the processing chamber. In addition, thepurging step may be performed by evacuating the inside of the processingchamber.

As described above, when the protective film 302 is formed using theinhibitor, the formation position or the film thickness of theprotective film 302 may be further adjusted. Further, the formationposition of the protective film 302 may be controlled in the same manneras described in the first embodiment. Thus, according to the secondembodiment, the inhibitor is used so that the protective film 302 may beprevented from being formed on the top, and furthermore, the processingconditions are adjusted so that the protective film 302 may be preventedfrom being formed on the lower portion of the side wall. As a result,according to the second embodiment, it is possible to more effectivelyprevent the opening from being closed when the protective film isformed, in addition to the effect obtained in the first embodiment.

FIGS. 12A, 12B, and 13A to 13E are views for explaining the suppressionof the closing of the opening by the substrate processing methodaccording to the second embodiment. FIGS. 12A and 12B represent the CDsizes corresponding to the depth direction from the interface betweenthe mask and the etching target film, in the pattern of the workpiece inthe initial state and after the film formation. In addition, when adifference between the CD size in the initial state and the CD sizeafter the film formation is divided by 2, the obtained value representsan amount of the film formation performed on the side wall (one side) ofthe pattern. In FIG. 12A, the dashed line represents the initial stateof the workpiece. The alternate long and short dash line represents aresult obtained when the film formation is performed on the workpiece inthe initial state by the normal ALD (Reference Example 1). The solidline represents a result obtained when the inhibitor layer is formed onthe workpiece in the initial state by the plasma CVD, and then, the filmformation is performed by the normal ALD (Reference Example 2). Inaddition, in FIG. 12B, the dashed line represents the initial state ofthe workpiece. The alternate long and short dash line represents aresult obtained when the film formation is performed on the workpiece inthe initial state by the substrate processing method according to thefirst embodiment (Example 1). The solid line represents a resultobtained when the film formation is performed on the workpiece in theinitial state by the substrate processing method according to the secondembodiment (Example 2).

As illustrated in FIG. 12A, when the film formation is performed by thenormal ALD, the formation of the protective film to the depth of about0.6 μm below the mask is suppressed by using the inhibitor layer.However, a substantially conformal protective film is formed atpositions deeper than about 0.6 μm. Meanwhile, as illustrated in FIG.12B, when the film formation is performed by the substrate processingmethod according to the second embodiment, the thickness of theprotective film to the depth of about 0.6 μm below the mask issuppressed to be about one half by using the inhibitor layer, andfurthermore, the formation of the protective film at positions deeperthan about 0.6 μm is suppressed as in a case where the inhibitor layeris not used. In this way, the film thickness of the protective film onthe top of the pattern may be more finely suppressed by using theinhibitor layer. In addition, the difference in film thickness of theprotective film in the depth direction of the pattern may be maintained.

In addition, FIGS. 13A to 13E schematically represent states of anopening in the top of the mask in the initial stage, Reference Examples1 and 2, and Examples 1 and 2 of FIGS. 12A and 12B, respectively. In theinitial state, the opening dimension near the top of the mask is about45 nanometers (nm). Meanwhile, when the film formation is performed bythe normal ALD (Reference Example 1), the opening dimension is reducedto about 30 nm. Meanwhile, when the inhibitor layer is formed, and then,the film formation is performed by the normal ALD (Reference Example 2),the opening dimension is maintained at about 42 nm. Meanwhile, when thefilm formation is performed by the substrate processing method accordingto the first embodiment (Example 1), the opening dimension is about 21nm. Meanwhile, when the inhibitor layer is formed, and then, the filmformation is performed by the substrate processing method according tothe second embodiment (Example 2), the opening dimension is maintainedat about 40 nm. Accordingly, the effect in preventing the closing of theopening by suppressing the film formation near the top of the mask usingthe inhibitor layer as in the second embodiment is confirmed.

Further, in the second embodiment, the protective film may be formed atan arbitrary position by adjusting the formation position of theinhibitor layer. Accordingly, it is possible to form the protective filmat a desired position while adjusting the film thickness of theprotective film to respond to the shape abnormality of the pattern thatis expected to occur, such as bowing or necking. Further, the positionof the film formation on the side wall may be adjusted by giving theaspect dependence to the position where the inhibitor layer is to beformed. Further, by changing the composition of the inhibitor layer,both the adsorption of the precursor and the reaction of the reactiongas in the ALD may be inhibited. For example, when an inhibitor layercontaining carbon is formed, the oxidation may be inhibited, and when aninhibitor layer containing CF is formed, the adsorption of the precursormay be inhibited.

Third Embodiment

In the first and second embodiments, the film formation is performed bychanging the coverage in the height direction of a pattern with a highaspect ratio. However, the present embodiment may be applied not only toa pattern with a high aspect ratio but also a pattern with a low aspectratio, for example, a pattern with an aspect ratio of less than 5.Accordingly, the embodiment applicable to the pattern with the lowaspect ratio will be described as a third embodiment. In the followingdescription, the “low aspect ratio” refers to an aspect ratio of lessthan 5.

FIGS. 14A to 14E are views for explaining a substrate processing methodaccording to the third embodiment. The workpiece of FIGS. 14A to 14Eincludes the etching target film 102 and the mask 120 which are stackedon the substrate 101, as in the workpiece S illustrated in FIGS. 3A to3D.

First, a workpiece in which a pattern with an aspect ratio of less than5 is formed on the etching target film 102 is prepared (FIG. 14A). Atthis time, the aspect ratio calculated from the upper surface of themask 120 may be less than 5, and the aspect ratio calculated from theupper surface of the etching target film 102 may be about 1 to 2.

Next, a processing is performed to reduce the opening dimension of theopening 200 formed in the workpiece, that is, to narrow the width of thetop 200T. For example, a preliminary film 303 is formed on the upperportion of the side wall 200S by a chemical vapor deposition (CVD) or aphysical vapor deposition (PVD). The preliminary film 303 is formedusing the processing condition that the preliminary film 303 is mainlyformed on the upper portion of the side wall 200S, and is not formed onthe lower portion of the side wall 200S and the bottom 200B (FIG. 14B).

Next, as in the first embodiment, a protection film 304 is formed by theALD using the condition that the processing is ended in a state wherethe adsorption of the precursor or the reaction of the reaction gas isunsaturated, that is, is not completed to the bottom surface. At thistime, the protective film 304 is formed on the side wall 200S, and isnot formed on the bottom 200B (FIG. 14C).

Next, the etching target film 102 is etched (FIG. 14D). When the depthdimension of the recess reaches a preset dimension or when theprocessing time for the etching reaches a preset processing time, theetching is ended. The timing for ending the etching may be setarbitrarily.

Next, the preliminary film 303 and the protective film 304 that remainon the top 200T and the upper portion of the side wall 200S are removed(FIG. 14E).

In this way, according to the substrate processing method according tothe third embodiment, the etching is performed after the protective film304 is coated to the position where the shape abnormality such as, forexample, bowing occurs, that is, to the portion of the etching targetfilm 102 immediately below the mask 120, so that the shape abnormalitysuch as bowing may be suppressed.

Further, according to the substrate processing method according to thethird embodiment, a sub-conformal ALD film may be formed on the patternwith the small aspect ratio, for example, an aspect ratio of less than5. In the first and second embodiments, when the protective film isformed on the pattern having the high aspect ratio, the film formationamount is controlled to gradually decrease from the upper portion to thelower portion of the side wall. However, when the aspect ratio of thepattern formed on the workpiece is small, the precursor and the reactiongas reach the bottom of the recess in a short time. Thus, it isdifficult to form the sub-conformal ALD film on the pattern with the lowaspect ratio. Meanwhile, when the CVD or PVD is used for the patternwith the low aspect ratio, it is difficult to finely control the filmthickness.

Accordingly, in the third embodiment, when the aspect ratio of thepattern formed on the workpiece is small, the processing of reducing theopening dimension of the pattern is performed in advance (FIG. 14B).With this processing, the aspect ratio of the pattern is increased, andthe amounts of the precursor and the reaction gas that enter the openingare suppressed. As a result, according to the third embodiment, thesub-conformal ALD film may be formed for the pattern with the low aspectratio as well, so that the fine control of the film thickness may beachieved.

FIG. 15 is a flowchart illustrating an example of flow of the substrateprocessing method according to the third embodiment. First, a workpieceis provided in which the mask 120 is formed on the etching target film102, and a pattern for etching is formed on the mask 120 (step S1501). Aworkpiece in a state where no pattern is formed may be introduced intothe chamber, and partially etched to form a pattern on the mask. Next,the etching target film 102 is etched (step S1502). It is determinedwhether the depth of the recess formed in the etching target film 102after the etching reaches a predetermined value (step S1503). When it isdetermined that the depth of the recess does not reach the predeterminedvalue (step S1503, No), the process returns to step S1502 to repeat theetching. Meanwhile, when it is determined that the depth of the recessreaches the predetermined value (step S1503, Yes), it is determinedwhether the aspect ratio of the recess is equal to or more than apredetermined value (e.g., 10) (step S1504). When it is determined thatthe aspect ratio of the recess is less than the predetermined value(step S1504, No), the preliminary film 303 is formed to narrow the widthof the opening 200 (step S1505). Then, the process returns to stepS1504. Meanwhile, when it is determined that the aspect ratio of therecess is equal to or more than the predetermined value (step S1504,Yes), the protection film 304 is formed (step S1506). The processing forforming the protective film 304 is the same as the processing forforming the protective film in the first embodiment. For example, theprotective film 304 may be formed by performing steps S101 to S105 inFIG. 1 . After the protective film 304 is formed, the etching isperformed again (step S1507). Then, it is determined whether theworkpiece has a predetermined shape (step S1508). For example, it isdetermined whether the depth of the recess formed in the etching targetfilm 102 by the etching has reached a predetermined depth. Then, when itis determined that the workpiece does not have the predetermined shape(step S1508, No), the process returns to step S1504 to repeat theprocessing. Meanwhile, when it is determined that the workpiece has thepredetermined shape (step S1508, Yes), the process is ended. In thisway, the substrate processing method according to the third embodimentis ended.

As described above, in the third embodiment, the protective film may beformed by the sub-conformal ALD even for the pattern with the low aspectratio, by performing the processing of narrowing the opening in advancethereby increasing the aspect ratio.

Further, in the third embodiment, the “low aspect ratio” is defined tobe the aspect ratio of less than 5, and the process according to thethird embodiment is applied to the pattern with the low aspect ratio.However, even when a pattern has an aspect ratio of 5 or more, it may bedifficult to implement the sub-conformal film formation as long as theaspect ratio is less than 10. Thus, the method of the third embodimentmay be applied to a pattern with an aspect ratio of 5 to 10.

In addition, the preliminary film 303 is preferably formed of a materialthat may be removed in a subsequent processing. For example, thepreliminary film 303 is formed of SiO₂, SiN, SiC or the like. When thepreliminary film 303 is formed of SiO₂, an aminosilane-based gas, SiCl₄,SiF₄ or the like may be used as the precursor. In addition, when thepreliminary film 303 is formed of SiN, an aminosilane-based gas, SiCl₄,DCS, HCDS or the like may be used as the precursor. Further, forexample, the preliminary film 303 may be an organic film such as acarbon-containing film, or a metal film containing titanium (Ti) ortungsten (W).

Modification 1—Change of Processing Conditions according to MaskThickness

The first and second embodiments have been described. Each of theembodiments may be further modified. FIG. 16 is a flowchart illustratingan example of flow of a substrate processing method according toModification 1. FIGS. 17A to 17D are views for explaining an example ofa workpiece processed by the substrate processing method according toModification 1. Modification 1 copes with a decrease of the filmthickness of the mask in the process of processing the workpiece basedon the methods of the first and second embodiments.

A workpiece S1 illustrated in FIG. 17A has the same shape as theworkpiece S illustrated in FIGS. 2A to 2D. In the substrate processingmethod according to Modification 1, the process from providing theworkpiece S1 (step S100) to performing the etching (step S106) is thesame as that in the first embodiment. By the process from step S100 tostep S106, for example, the workpiece S1 illustrated in FIG. 17B isformed. As for the workpiece S1, an etching target film 102A and a mask120A are formed on a substrate 101A. Further, a recess having an opening200A is formed in the etching target film 102A and the mask 120A. Aprotective film 130A is formed on the top of the recess and the upperportion of the side wall. The protective film 130A is formed to theposition immediately below the mask 120A where the shape abnormality mayeasily occur due to the etching. Further, the inner wall of theprotective film 130A is shaved by the etching. When steps S101 to S106are repeated again from the state represented in FIG. 17B, the top ofthe mask 120A is gradually shaved, and the distance from the top of themask 120A to the upper surface of the etching target film 102A changes(FIG. 17C). In this case, when the protective film 130A is formedwithout changing the processing conditions of the first and secondsteps, the position where the protective film 130A is formed becomeslower than the position immediately below the mask 120A where the shapeabnormality occurs.

Accordingly, in Modification 1, after the etching (step S106) and stepS107 are performed, it is determined whether the film thickness of themask 120A is a predetermined value (step S108). The determination ofwhether the film thickness of the mask 120A is the predetermined valuemay be performed based on the film thickness of the mask 120A before theworkpiece S1 is processed and the number of times that steps S101 toS106 are performed. In addition, the determination of whether the filmthickness of the mask 120A is the predetermined value may be performedbased on a measured value of the film thickness. In addition, the methodof measuring the film thickness is not particularly limited, and thefilm thickness may be measured by, for example, an optical method. Then,when it is determined that the film thickness of the mask 120A is thepredetermined value (step S108, Yes), the processing conditions of thefirst step or the second step are reset (step S109). For example, whenthe processing conditions are set to change the coverage in the firststep along the depth direction of the pattern, the processing conditionsare changed to cause the first gas to be adsorbed to the further upperportion of the pattern. For example, the processing time for the nextfirst step is set to be shorter than the processing time for theprevious first step. In addition, for example, when the processingconditions are set to change the coverage in the second step along thedepth direction of the pattern, the processing conditions are changed tocause the second gas to react only at the further upper portion of thepattern. For example, the temperature of the processing chamber is setto be low. Meanwhile, when it is determined that the film thickness ofthe mask 120A is not the predetermined value (step S108, No), theprocess returns to step S101 without changing the processing conditions.

As described above, by adjusting the processing conditions according tothe film thickness of the mask 120A, the protective film 130A may beselectively formed at the position where the shape abnormality mayeasily occur. For example, in the workpiece of FIG. 17C, the filmthickness of the mask 120A becomes about half that at the start time ofthe processing, and thus, the distance from the top to the etchingtarget film 102A is short. In this case, the processing conditions arechanged to reduce the distance in the depth direction in which theprotective film 130A is formed. Then, as illustrated in FIG. 17D, theprotective film 130A may be continuously formed at the positionimmediately below the mask 120A where the shape abnormality may easilyoccur.

In addition, even when bowing occurs in the etching target film 102A,the pattern shape may be corrected by updating the processing conditionsand performing steps S101 to S104.

As described above, when the aspect ratio of the recess having theopening 200A increases due to the etching (step S106) performed afterthe first and second steps, the processing conditions may be changed.For example, the processing conditions of at least one of the first step(step b-1) and the second step (step b-2) may be changed according tothe increase of the aspect ratio. For example, the transport amount ofradicals generated in the second step may be increased. That is, theprocessing conditions may be changed such that as the number of times ofetching (step S106) increases, the protective film 130A is formed on thefurther upper portion of the etching target film 102A. In addition, theprocessing conditions may be changed each time the first and secondssteps are repeated, or may be changed after the first and second stepsare repeated several times. In addition, the processing conditions maybe appropriately changed according to factors other than the filmthickness of the mask.

Fourth Embodiment

As described in the first embodiment, in a case where a recess is formedto have a diameter that is reduced from the top toward the bottom, acontrol may be implemented to increase the dimension of the bottom whilesuppressing the change of the dimension of the side wall by theprotective film (see paragraph [0069]). The control of the dimension ofthe recess will be further described as a fourth embodiment. Accordingto a substrate processing method of the fourth embodiment, the degree offreedom in controlling the shape of the pattern to be formed may beimproved.

FIG. 18 is a flowchart illustrating an example of a flow of thesubstrate processing method according to the fourth embodiment. FIGS.19A to 19D and 20A to 20D are views illustrating an example of aworkpiece processed by the substrate processing method according to thefourth embodiment.

First, a workpiece S2 (see FIG. 19A) is provided (step S1800). Theworkpiece S2 includes a substrate 101B, an etching target film 102Bformed on the substrate 101B, and a mask 120B (see FIG. 19A). The mask120B has an opening 200A′. The opening 200A′ has a bottom 201 and a sidewall 202. The bottom 201 of the opening 200′ reaches the etching targetfilm 102B. In step S1800, the etching target film 102B is partiallyetched via the mask 120B.

Next, as in the first embodiment, the protective film 130A is formed bythe first step (step S1801), the purging (step S1802), the second step(step S1803), and the purging (step S1804) (see FIGS. 17A to 17D). Then,when it is determined that the protective film 130A has a predeterminedfilm thickness (step S1805, Yes), the workpiece S2 is etched (stepS1806). Meanwhile, when it is determined that the protective film 130Adoes not have the predetermined film thickness (step S1805, No), theprocess returns to step S1801 to repeat the processing. Steps S1801 toS1806 are the same as steps S101 to S106 in FIG. 16 , and the purging ineach of steps S1802 and S1804 may be omitted. Further, in the presentembodiment, steps S1801 to S1804 may be omitted in a case where thebowing described in the first embodiment does not occur or the influenceof the bowing is small when the workpiece S2 is etched in steps S1806.

Next, it is determined whether the depth of the opening 200A′ formed inthe workpiece S2 reaches a predetermined value (step S1807). Forexample, it is determined whether the depth of the opening 200A′ reachesthe position of the upper surface of the substrate 101B. When it isdetermined that the depth of the opening 200A′ does not reach theposition of the upper surface of the substrate 101B (step S1807, No),the process returns to step S1805 to repeat the processing. Meanwhile,when it is determined that the depth of the opening 200A′ reaches theposition of the upper surface of the substrate 101B (step S1807, Yes),it is determined whether the opening dimension of the bottom 201 isequal to or larger than a predetermined value (step S1808). The openingdimension of the bottom 201 refers to a horizontal dimension of thebottom 201. Hereinafter, the horizontal dimension of the bottom 201 mayalso be referred to as a bottom CD (critical dimension). The“predetermined value” in each of steps S1807 and S1808 is set in advancebased on, for example, a design of an apparatus.

Here, it is assumed that the opening 200A′ has an ideal shape in whichthe side wall 202 extends vertically from the top to the bottom 201.Further, it is assumed that the “predetermined value” in step S1808 isset as the bottom CD of the ideal shape. Further, it is assumed that thetapered opening 200A′ illustrated in FIG. 19B is formed. In this case,in step S1808, it is determined that the bottom CD is less than thepredetermined value (step S1808, No). When it is determined that thebottom CD is less than the predetermined value, the protective film 130Bis formed (step S1809, see FIG. 19C). The protective film 130B is formedon the top 203 and the side wall 202 of the opening 200A′. In theexample of FIG. 19C, the protective film 130B is formed to have a filmthickness that gradually decreases from the upper portion toward thelower portion of the side wall 202. As a method of forming theprotective film 130B, the sub-conformal ALD that is used for forming theprotective film 130A (see FIGS. 17A to 17D) and others may be used, orthe plasma CVD (PECVD) may be used. When the PECVD is used, for example,SiCl₄, O₂ and a rare gas may be used as the processing gas. As the raregas, for example, Ar, He, and Kr may be used. Further, the pressure inthe chamber may be 10 mTorr to 1 Torr, and the radio frequency (RF)power may be 50 W or more.

Next, the workpiece S2 on which the protective film 103B is formed isetched (trimmed) (step S1810). At this time, the portion of the sidewall 202 that is covered with the protective film 130B is not etched,and the lower portion of the side wall 202 that is not covered with theprotective film 130B or has the thinner film thickness of the protectivefilm 130B than that in the upper portion has the larger width than thatof the upper portion as a result of the etching (see FIG. 19D). Afterthe etching in step S1801, the process returns to step S1808.

In step S1808, when it is determined that the bottom CD is equal to ormore than the predetermined value (step S1808, Yes), for example, whenthe predetermined value in step S1808 is set to be substantiallyidentical to the dimension of the top of the opening, the shape of theworkpiece S2 at the time when the process is ended becomes, for example,the shape illustrated in FIG. 19D.

The etching of step S1806 and the etching of step S1810 are performedunder different processing conditions. In the etching of step S1806,processing conditions are set such that the opening 200A′ is dug mainlyin the depth direction. Meanwhile, in the etching of step S1810,processing conditions are set such that the bottom 201 of the opening200A′ is expanded in the horizontal direction. For example, theprocessing conditions in step S1806 are set to implement an anisotropicetching, and the processing conditions in step S1810 are set toimplement an isotropic etching. The processing of step S1810 may beimplemented using, for example, COR (chemical oxide removal) which is amethod according to Modification 3 to be described later, instead of theetching.

For example, when the etching target film 102B is a silicon oxide film(SiO₂), a fluorocarbon (CF)-based etching gas is used in the etching ofstep S1806. For example, C₄F₆, C₄F₈ or the like may be used. Inaddition, a mixture of a CF-based gas, argon (Ar) gas, and oxygen (O₂)gas may be used. In addition, a hydrofluorocarbon (CHF)-based etchinggas such as CH₃F, CH₂F₂ and CHF₃ may be added. Meanwhile, in the etchingof step S1810, a fluorine-containing gas may be used as the etching gas.For example, NF₃ may be used.

Further, for example, when the etching target film 102B is an organicfilm, an oxygen-containing gas may be used in the etching of step S1806.For example, O₂ , CO, CO₂ or the like may be used as the etching gas. Inthis case, an oxygen-containing gas may also be used as the etching gasin step S1810.

In addition, as for the other processing conditions than the processinggas, it is preferable that the pressure of the chamber in the processingof step S1806 is about 10 mTorr to 30 mTorr, and the pressure of thechamber in the processing of step S1810 is 100 mTorr or more. Further,the radio frequency (RF) voltage applied for bias generation at the timeof generating plasma is set to be higher in the processing of step S1806than that in the processing of step S1810.

In addition, when the method of Modification 3 is used in step S1810, amixed gas of a fluorine-containing gas and NH₃ or a mixed gas of N₂ andH₂ may be used. As the fluorine-containing gas, NF₃, SF₆ or a CF-basedgas may be used.

As described above, in the substrate processing method according to thefourth embodiment, after an opening having a desired depth is formed, afilm having a thickness that differs along the depth direction of theopening is formed, and the workpiece is etched. Thus, the dimension ofthe lower portion of the opening that is not covered with the film maybe expanded in the horizontal direction, and the dimension of theopening may be adjusted. As a result, according to the fourthembodiment, it is possible to more finely suppress the shape abnormalityof the pattern in the etching target film.

In addition, the substrate processing method according to the fourthembodiment may be performed not only after the bottom 201 of the opening200A′ reaches the position of the upper surface of the substrate 101B,but also during the etching of the etching target film 102B. FIGS. 20Ato 20D illustrate an example where the substrate processing methodaccording to the fourth embodiment is applied during the etching of theetching target film 102B.

The workpiece S2 illustrated in FIG. 20A is the same as the workpiece S2illustrated in FIG. 19A. The shape represented in FIG. 20B may beobtained in the middle of the step of digging the opening 200A′ startingfrom the state of FIG. 19A until the opening 200A′ becomes the state ofFIG. 19B. For example, the “predetermined value” in step S1807 of FIG.18 is set to a depth that does not reach the substrate 101B. Then, stepS1808 is performed in a step where the bottom 201 of the opening 200A′is positioned inside the etching target film 102B. Further, step S1808is performed based on, for example, the performance time of steps S1800and S1806, in the step where the bottom 201 of the opening 200A′ ispositioned inside the etching target film 102B. Then, the formation ofthe protective film in step S1809 (see FIG. 20C) and the etching in stepS1810 (see FIG. 20D) are performed in the state represented in FIG. 20B.By altering the determination process in this way, the process ofexpanding the bottom CD may be started from the state represented inFIG. 20B. As a result, the shape of the opening 200A′ may be adjustedwhile suppressing the damage to the substrate 101B.

As described above, in the substrate processing method according to thefourth embodiment, the protective film 130B may be formed from the timewhen the bottom 201 of the opening 200A′ is positioned inside theetching target film 102B. Thus, according to the fourth embodiment, thereduction of the bottom CD may be suppressed, and further, theoccurrence of bowing may be suppressed.

Determination of Bottom CD

The determination method in step S1808 is not limited. For example, thebottom CD may be determined by inspecting the shape of the workpiece S2using optical means or the like. In addition, the bottom CD may bedetermined based on the number of times of performing steps S1801 toS1804 and S1806 or the performance time of the steps. In addition, whenstep S1810 is performed, the bottom CD may be determined based on theperformance time of step S1810. The “predetermined value” in step S1808is set in advance based on a design value.

Determination of Whether to Form Protective Film

In addition, it may be determined whether to form the protective film(step S1809), before step S1809. The determination method is notparticularly limited. For example, it may be determined whether to formthe protective film 130B, according to the thickness and/or the positionof the protective film 130B remaining on the side wall 202. Further, itmay be determined whether to form the protective film 130B, accordingto, for example, the number of times of performing steps S1801 to S1804and S1806 or the performance time of the steps. In addition, when theprotective film formed in steps S1801 to S1804 (130A in FIGS. 17A to17D) remains, it may be determined whether to perform step S1809,according to the thickness and/or the position of the protective film.

The determination in step S1808 and the determination of whether to formthe protective film may be performed collectively. For example, theprocess may be ended when the number of times of performing steps S1801to S1804 and S1806 reaches a value V1. Further, when the number of timesof performing steps S1801 to S1804 and S1806 does not reach a value V2(V2<V1), the protective film 130B may be formed. In addition, when thenumber of times of performing steps S1801 to S1804 and S1806 does notreach a value V3 (V3<V2), the etching (S1810) may be performed withoutforming the protective film 130B.

Film Types

The type of each of the etching target film 102B, the mask 120B, and theprotective film 130B is not particularly limited. For example, thesubstrate 101B may be a silicon wafer. The etching target film 102B maybe a dielectric film, for example, a silicon-containing dielectric film.The etching target film 102B may be formed by stacking a plurality oftypes of films. For example, the etching target film 102B may be a layerin which a silicon oxide film and a silicon nitride film are stacked inan order. The etching target film 102B may be a layer in which a siliconoxide film and a polysilicon film are stacked in an order. The mask 120Bmay be a carbon-containing film. The carbon-containing film may beformed of an amorphous carbon layer (ACL) or a spin-on carbon film(SOC). Alternatively, the mask 120B may be formed of a metal film. Inaddition, although not illustrated in FIGS. 19A to 19D and 20A to 20D, asilicon oxynitride film (SiON) or a back surface antireflection film(BARC) having the same opening pattern as that of the mask 120B may bepresent on the mask 120B. The protective film 130B may be asilicon-containing film. In addition, the film types of the mask 120Band the etching target film 102B may be the same.

In the substrate processing method according to the fourth embodiment,when the etching target film 102B is a silicon-containing dielectricfilm, the mask 120B may be a carbon-containing film such as ACL and SOC.In addition, when the etching target film 102B is a polysilicon film,the mask 120B may be, for example, a silicon oxide film formed usingTEOS (tetraethoxysilane).

In the substrate processing method according to the fourth embodiment,plasma may or may not be used for forming the protective film in stepS1809 and performing the etching in step S1810.

In addition, the substrate processing method according to the fourthembodiment may be applied to not only a pattern with a high aspect ratiobut also patterns with various aspect ratios including a low aspectratio. The substrate processing method according to the fourthembodiment may be preferably applied to, for example, a pattern with anaspect ratio of 10 to 20.

Modification 2—Adjustment of Film Thickness in Wafer Plane

In the first embodiment, the coverage and the film thickness of theprotective film are adjusted by adjusting the processing conditions.Meanwhile, the processing conditions in the first and second steps maybe adjusted from the following two viewpoints.

(1) The position of the film formation in the depth direction of thepattern is controlled by controlling the introduction amount of theprecursor or reaction gas.

(2) The film thickness of the protective film to be formed iscontrolled.

In the first and second embodiments, the position of the film formationis controlled mainly from the viewpoint (1). Modification 2 adjusts theprocessing conditions from the viewpoint (2). FIGS. 21A and 21B areviews for explaining a relationship between the temperature of theworkpiece and the film formation amount. A wafer processed in asubstrate processing apparatus has, for example, a disk shape with adiameter of about 300 mm. It is known that when a film formationprocessing is performed on the wafer, the film formation amount variesaccording to the temperature of the wafer. FIG. 21A represents therelationship between the temperature of the wafer and the film formationamount. As represented in FIG. 21A, when the temperature of the waferincreases, the film formation amount increases, and when the temperatureof the wafer decreases, the film formation amount decreases.

In Modification 2, the stage of the wafer (electrostatic chuck) isdivided into a plurality of concentric zones such that the temperatureof each zone may be independently controlled. Accordingly, the filmthickness of the protective film to be formed at an arbitrary positionmay be controlled to be a desired thickness. For example, it is knownthat during a processing such as etching, the shape abnormality (e.g.,bowing) is small at the center of the wafer and large at the edge of thewafer. In this case, the temperature of the center where the shapeabnormality tends to be small is controlled to be lower than thetemperature of the edge where the shape abnormality tends to be large.With this control, the film thickness of the protective film to beformed may be adjusted according to the radial position of the wafer,and the in-plane uniformity of the dimension of an opening to be formedmay be improved.

In addition, for the control of the film thickness, when the pluralityof zones divided in the radial direction and in the circumferentialdirection are formed such that the temperature of each zone may beindependently controlled as illustrated in FIG. 21B, the temperaturecontrol may be used, in addition to the improvement of the in-planeuniformity. For example, it is possible to implement a processing offorming openings having different shapes by changing the thickness of aprotective film to be formed on each position of the wafer.

Modification 3—Removal of Oxide Film

When semiconductor devices are manufactured, a natural oxide film may beformed on a wafer W. The natural oxide film may be removed, and in thatcase, other peripheral films may be removed or damaged. Thus, it ispreferable to remove the natural oxide film without damaging theperipheral films. The substrate processing method according to thepresent embodiment may change the film formation amount in the depthdirection of the pattern. Thus, it is possible to suppress the damage tothe peripheral films when the natural oxide film is removed, by notforming a protective film on the oxide film formed on the bottom of therecess and by forming a protective film on other portions.

FIGS. 22A to 22C are views for explaining an example of a workpieceprocessed by a substrate processing method according to Modification 3.FIG. 22A is a view illustrating an example of a workpiece on which anoxide film is formed. As for the workpiece (e.g., a semiconductor waferW), a SiO₂ film 140 is formed on a silicon (Si) layer 101C that servesas a base. A pattern is formed on the SiO₂ film 140. In FIGS. 22A to22C, a recess is formed as a pattern in the SiO₂ film 140 to reach theSi layer 101C. In the workpiece, the upper surface of the SiO₂ film 140and the side wall of the recess are covered with a SiN film 150.Further, in the wafer W, a natural oxide film 160 (SiO₂) is formed onthe Si layer 101C of the bottom of the recess. Since the portion of thenatural oxide film 160 that corresponds to the bottom of the recess isshifted to silicon germanium or the like, the Si layer 101C isrepresented in a different pattern.

In the substrate processing method according to Modification 3, theprotective film 300C of which film thickness becomes thin in the depthdirection is formed on the side wall of the recess, by using steps S101to S104 of the first embodiment. In the substrate processing methodaccording to the first embodiment, the film formation is not performedon the bottom of the recess, and is performed on the side wall and thetop. As a result, the protective film 300C illustrated in FIG. 22B maybe formed. Then, an etching is performed after the protective film 300Cis formed. Since the protective film 300C covers the side wall, the SiNfilm 150 below the protective film 300C may be suppressed from beingdamaged, and the natural oxide film 160 on the bottom and the protectivefilm 300C on the side wall may be removed. As a result, the workpieceillustrated in FIG. 22C is obtained.

As described above, when the protective film 300C is formed using thesub-conformal ALD, the film is not formed on the bottom of the recessand is formed on the side wall and the top of the recess, so that thenatural oxide film 160 may be removed without lowering the etching rateof the bottom of the recess. Further, by forming the protective film300C on the side wall of the recess, the damage to the SiO₂ film 140 orthe SiN film 150 may be suppressed.

In the embodiments described above, an example where the protective filmis used to suppress the occurrence of the shape abnormality of asemiconductor pattern has been described. The present disclosure is notlimited thereto, and the substrate processing method according to theembodiments may be used to correct the shape abnormality when the shapeabnormality occurs in a mask during a formation of a pattern.

Conditioning in Chamber

In the embodiments described above, for example, the film formation insteps S101 to S104 of FIG. 1 and the etching in step S106 of FIG. 1 maybe performed in one chamber. In this case, by-products generated by theetching may adhere to the inside of the chamber, and may affect theconditions for the film formation. Meanwhile, when only a processing offorming the same film is performed in one chamber, the same film as thefilm formed on the workpiece is additionally formed on the inner wall ofthe chamber and the surfaces of other components. Thus, the state of afilm formed by a film formation may differ between a case where only thefilm formation is performed in one chamber and a case where both thefilm formation and the etching are performed in one chamber.

Accordingly, after the etching of the present embodiment (e.g., stepS106 in FIG. 1 ) is performed, conditioning of the surface exposed tothe plasma space in the chamber may be performed. As the conditioning,(1) cleaning in the chamber and (2) coating in the chamber may beperformed.

The cleaning in the chamber is performed by, for example, turning apredetermined cleaning gas into plasma in the chamber, and then,discharging the plasma. As the cleaning gas, an oxygen-containing gassuch as O₂ or CO₂, or a hydrogen-containing gas such as H₂ or NH₃ may beused. In addition, the cleaning method is not particularly limited. Thecleaning in the chamber is performed under, for example, a conditionthat carbon or fluorine adhering onto the outermost surface (the innersurface of the chamber) is removed.

In addition, the coating in the chamber is performed by turning apredetermined coating gas into plasma in the chamber, and then,discharging the plasma. As for the coating gas, a silicon oxide filmSiO₂ or the like may be formed by the CVD or ALD using asilicon-containing gas such as SiCl₄ or an aminosilane-based gas, or anoxygen-containing gas such as O₂. The coating method is not particularlylimited. Further, the material used for the coating is not alsoparticularly limited. The coating is performed, for example, after aplasma processing using fluorine (e.g., CF) is performed. With thecoating, by-products exposed to the uppermost surface of the chamber arecovered and prevented from being exposed to the plasma processing space.

In addition, the cleaning and the coating for the conditioning areperformed under the condition that not only the periphery of the stageon which the workpiece is disposed but also the entire inner wall of thechamber are processing targets. In addition, the cleaning and thecoating for the conditioning may be performed for every plasmaprocessing, or may be performed each time the plasma processing isperformed a predetermined number of times. As a result, the innersurface to which by-products adhere is prevented from being exposed tothe plasma processing space. Thus, the condition and the state in thechamber are prevented from being changed for each processing, so thatthe state of the film to be formed may be stabilized.

Other Modifications

In the embodiment described above, the first and second steps may be setas one cycle, and the cycle may be repeated an arbitrary number oftimes. Further, in the embodiment described above, the film formed bythe ALD has been described as an example of the film having theself-controllability. However, the present disclosure is not limitedthereto, and for example, a self-assembled monolayer (SAM) may be usedas the protective film.

Example of Substrate Processing Apparatus according to Embodiment

FIG. 23 is a view illustrating an example of a substrate processingapparatus according to an embodiment, which is used for performing thesubstrate processing method according to the embodiment described above.FIG. 23 schematically illustrates a cross-sectional structure of asubstrate processing apparatus 10 which is usable in the variousembodiments of the substrate processing method according to theembodiment described above. As illustrated in FIG. 23 , the substrateprocessing apparatus 10 is a plasma etching apparatus provided withparallel plate electrodes, and includes a processing container 12. Theprocessing container 12 has a substantially cylindrical shape, anddefines a processing space Sp. The processing container 12 is made of,for example, aluminum, and an inner wall surface of the processingcontainer 12 is anodized. The processing container 12 is grounded forsecurity.

A substantially cylindrical support 14 is provided on the bottom of theprocessing container 12. The support 14 is made of, for example, aninsulating material. The insulating material of the support 14 mayinclude oxygen like quartz. The support 14 extends vertically from thebottom of the processing container 12 in the processing container 12. Astage PD is provided inside the processing container 12. The stage PD issupported by the support 14.

The stage PD holds a wafer W on the top surface thereof. The mainsurface FW of the wafer W is present on the opposite side of the backsurface of the wafer W in contact with the top surface of the stage PD,and faces an upper electrode 30. The stage PD includes a lower electrodeLE and an electrostatic chuck ESC. The lower electrode LE includes afirst plate 18 a and a second plate 18 b. The first plate 18 a and thesecond plate 18 b are formed of, for example, a metal such as aluminum,and has a substantially disk shape. The second plate 18 b is provided onthe first plate 18 a, and electrically connected to the first plate 18a.

The electrostatic chuck ESC is provided on the second plate 18 b. Theelectrostatic chuck ESC has a structure in which an electrode serving asa conductive film is disposed between a pair of insulating layers orbetween a pair of insulating sheets. A DC power supply 22 iselectrically connected to the electrode of the electrostatic chuck ESCvia a switch 23. When the wafer W is disposed on the stage PD, the waferW comes into contact with the electrostatic chuck ESC. The back surface(the surface opposite to the main surface FW) of the wafer W is incontact with the electrostatic chuck ESC. The electrostatic chuck ESCadsorbs the wafer W by an electrostatic force such as a Coulomb forcegenerated by a DC voltage from the DC power supply 22. As a result, theelectrostatic chuck ESC may hold the wafer W thereon.

An edge ring ER is provided on the circumferential edge of the secondplate 18 b to surround the edge of the wafer W and the electrostaticchuck ESC. The edge ring ER is provided to improve the uniformity ofetching. The edge ring ER is formed of a material appropriately selectedaccording to a material of a film to be etched, and may be formed of,for example, silicon or quartz.

A refrigerant flow path 24 is provided inside the second plate 18 b. Therefrigerant flow path 24 constitutes a temperature control mechanism. Arefrigerant is supplied to the refrigerant flow path 24 from a chillerunit (not illustrated) provided outside the processing container 12 viaa pipe 26 a. The refrigerant supplied to the refrigerant flow path 24 isreturned to the chiller unit through a pipe 26 b. In this way, therefrigerant is supplied to the refrigerant flow path 24 such that therefrigerant is circulated. By controlling the temperature of therefrigerant, the temperature of the wafer W supported by theelectrostatic chuck ESC may be controlled.

A gas supply line 28 is provided in the substrate processing apparatus10. The gas supply line 28 supplies a heat transfer gas, for example, Hegas, from a heat transfer gas supply mechanism to the space between thetop surface of the electrostatic chuck ESC and the back surface of thewafer W.

The substrate processing apparatus 10 is provided with a temperaturecontroller HT that controls the temperature of the wafer W. Thetemperature controller HT is mounted in the electrostatic chuck ESC. Aheater power supply HP is connected to the temperature controller HT. Apower is supplied from the heater power supply HP to the temperaturecontroller HT, so that the temperature of the electrostatic chuck ESC isadjusted, and the temperature of the wafer W disposed on theelectrostatic chuck ESC is adjusted. In addition, the temperaturecontroller HT may be embedded in the second plate 18 b.

The substrate processing apparatus 10 includes the upper electrode 30.The upper electrode 30 is disposed above the stage PD to face the stagePD. The lower electrode LE and the upper electrode 30 are providedsubstantially in parallel to each other, and constitute the parallelplate electrodes. The processing space Sp is provided between the upperelectrode 30 and the lower electrode LE to perform a processing on thewafer W.

The upper electrode 30 is supported on the upper portion of theprocessing container 12 via an insulating shielding member 32. Theinsulating shielding member 32 is made of an insulating material, andmay include, for example, oxygen like quartz. The upper electrode 30 mayinclude an electrode plate 34 and an electrode support 36. The electrodeplate 34 faces the processing space Sp, and a plurality of gas dischargeholes 34 a are formed in the electrode plate 34. In an embodiment, theelectrode plate 34 contains silicon. In another embodiment, theelectrode plate 34 may contain silicon oxide.

The electrode support 36 detachably supports the electrode plate 34, andmay be made of, for example, a conductive material such as aluminum. Theelectrode support 36 may have a water-cooled structure. A gas diffusionchamber 36 a is provided inside the electrode support 36. A plurality ofgas flow holes 36 b extend downward from the gas diffusion chamber 36 ato communicate with the gas discharge holes 34 a.

The substrate processing apparatus 10 includes a first radio-frequencypower supply 62 and a second radio-frequency power supply 64. The firstradio-frequency power supply 62 generates a first radio-frequency powerfor generating plasma, and generates a radio-frequency power of afrequency of 27 MHz to 100 MHz, for example, 60 MHz. In addition, thefirst radio-frequency power supply 62 has a pulse specification whichmay be controlled at a frequency of 0.1 kHz to 50 kHz and a duty of 5%to 100%. The first radio-frequency power supply 62 is connected to thelower electrode LE via a matching unit 66. The matching unit 66 is acircuit for matching the output impedance of the first radio-frequencypower supply 62 and the input impedance of a load side (the lowerelectrode LE side) with each other. In addition, the firstradio-frequency power supply 62 may be connected to the upper electrode30 via the matching unit 66.

The second radio-frequency power supply 64 generates a secondradio-frequency power for drawing ions into the wafer W, that is, aradio-frequency bias power, and generates a radio-frequency bias powerof a frequency in a range of from 400 kHz to 40.68 MHz, for example, afrequency of 13.56 MHz. In addition, the second radio-frequency powersupply 64 has a pulse specification which may be controlled at afrequency of 0.1 kHz to 50 kHz and a duty of 5% to 100%. The secondradio-frequency power supply 64 is connected to the lower electrode LEvia a matching device 68. The matching unit 68 matches the outputimpedance of the second radio-frequency power supply 64 and the inputimpedance of a load side (the lower electrode LE side) with each other.

The substrate processing apparatus 10 further includes a power supply70. The power supply 70 is connected to the upper electrode 30. Thepower supply 70 applies a voltage for drawing positive ions existing inthe processing space Sp into the electrode plate 34, to the upperelectrode 30. In an example, the power supply 70 is a DC power supplythat generates a negative DC voltage. When the voltage is applied fromthe power supply 70 to the upper electrode 30, the positive ionsexisting in the processing space Sp collide with the electrode plate 34.As a result, secondary electrons and/or silicon may be emitted from theelectrode plate 34.

An exhaust plate 48 is provided near the bottom of the processingcontainer 12 and between the support 14 and the side wall of theprocessing container 12. The exhaust plate 48 may be configured by, forexample, coating an aluminum material with ceramics such as Y₂O₃. Anexhaust port 12 e is provided below the exhaust plate 48 in theprocessing container 12. An exhaust device 50 is connected to theexhaust port 12 e via an exhaust pipe 52. The exhaust device 50 isprovided with a vacuum pump such as a turbo molecular pump, and iscapable of depressurizing the space inside the processing container 12to a desired degree of vacuum. A carry-in/out port 12 g of the workpieceW is provided in the side wall of the processing container 12, and isopenable/closable by a gate valve 54.

A gas source group 40 includes a plurality of gas sources. The pluralityof gas sources may include sources of various gases such as a source ofan organic-containing aminosilane-based gas, a source of afluorocarbon-based gas (CxFy gas (x, y are integers of 1 to 10)), asource of a gas having oxygen atoms (e.g., oxygen gas), and a source ofinert gas. As the inert gas, any gas such as nitrogen gas, Ar gas or Hegas may be used.

A valve group 42 includes a plurality of valves, and a flow ratecontroller group 44 includes a plurality of flow rate controllers suchas mass flow controllers. Each of the plurality of gas sources of thegas source group 40 is connected to a gas supply pipe 38 and a gassupply pipe 82 via a corresponding valve of the valve group 42 and acorresponding flow rate controller of the flow rate controller group 44.Accordingly, the substrate processing apparatus 10 is capable ofsupplying gases from one or more gas sources selected from the pluralityof gas sources in the gas source group 40, into the processing container12 at individually controlled flow rates.

A gas introduction port 36 c is provided in the processing container 12.The gas introduction port 36 c is provided above the wafer W disposed onthe stage PD in the processing container 12. The gas introduction port36 c is connected to one end of the gas supply pipe 38. The other end ofthe gas supply pipe 38 is connected to the valve group 42. The gasintroduction port 36 c is provided in the electrode support 36. The gassupplied from the gas introduction port 36 c to the processing space Spvia the gas diffusion chamber 36 a is supplied to the space region abovethe wafer W and between the wafer W and the upper electrode 30.

A gas introduction port 52 a is provided in the processing container 12.The gas introduction port 52 a is provided on the lateral side of thewafer W disposed on the stage PD in the processing container 12. The gasintroduction port 52 a is connected to one end of the gas supply pipe82. The other end of the gas supply pipe 82 is connected to the valvegroup 42. The gas introduction port 52 a is provided in the side wall ofthe processing container 12. The gas supplied from the gas introductionport 52 a to the processing space Sp is supplied to the space regionabove the wafer W and between the wafer W and the upper electrode 30.

In the substrate processing apparatus 10, a deposition shield 46 isdetachably provided along the inner wall of the processing container 12.The deposition shield 46 is also provided on the outer periphery of thesupport 14. The deposition shield 46 prevents etching by-products(deposit) from adhering to the processing container 12, and may beconfigured by coating an aluminum material with ceramics such as Y₂O₃.The deposition shield 46 may be made of, for example, a materialcontaining oxygen like quartz, other than Y₂O₃.

A controller Cnt is a computer provided with, for example, a processor,a storage unit, an input device, and a display device, and controls eachunit of the substrate processing apparatus 10 illustrated in FIG. 23 .

The controller Cnt operates according to a computer program (a programbased on an input recipe) for controlling each unit of the substrateprocessing apparatus 10 in each step of the substrate processing methodaccording to the embodiment, and sends out a control signal. Each unitof the substrate processing apparatus 10 is controlled by the controlsignal from the controller Cnt. Specifically, in the substrateprocessing apparatus 10 illustrated in FIG. 23 , the controller Cnt iscapable of controlling, for example, the selection and the flow rate ofa gas to be supplied from the gas source group 40, the exhaust by theexhaust device 50, the supply of power from the first radio-frequencypower supply 62 and the second radio-frequency power supply 64, theapplication of a voltage from the power supply 70, the supply of powerfrom the heater power supply HP, and the flow rate and the temperatureof the refrigerant from the chiller unit, by using control signals. Inaddition, each step of the substrate processing method disclosed hereinmay be performed by operating each unit of the substrate processingsystem 10 under the control by the controller Cnt. In the storage unitof the controller Cnt, the computer program for performing the substrateprocessing method according to the embodiment and various types of dataused for performing the method are stored in a readable manner.

Effects of Embodiment

The substrate processing method according to the embodiment describedabove includes steps (a) and (b). Step (a) forms a recess on a workpieceby partially etching the workpiece. Step (b) forms a film having athickness that differs along the depth direction of the recess, on theside wall of the recess. Step (b) includes steps (b-1) and (b-2). Step(b-1) supplies the first reactant to cause the first reactant to beadsorbed to the side wall of the recess. Step (b-2) supplies the secondreactant to cause the second reactant to react with the first reactantthereby forming a film. Thus, according to the embodiment, the filmthickness of the film to be formed on the pattern with the high aspectratio may be changed along the depth direction. Thus, according to theembodiment, it is possible to form the protective film in advance at theposition of the pattern where the shape abnormality may easily occur,while changing the film thickness of the protective film in the depthdirection. As a result, according to the embodiment, the shapeabnormality of a semiconductor pattern may be suppressed. Further,according to the embodiment, since the film having theself-controllability, for example, the ALD film is formed, the thicknessof the protective film to be formed may be precisely controlled. Thus,according to the embodiment, the opening of the pattern may besuppressed from being closed. Further, according to the embodiment, bysuppressing the protective film from being formed on the bottom of thepattern, the etching stop is prevented so that the etching rate may beimproved. Further, according to the embodiment, by adjusting theprocessing conditions of steps (b-1) and (b-2), the coverage of theprotective film along the depth direction of the pattern may be largelychanged.

Further, in the embodiment, step (b-1) of step (b) suppresses the firstreactant from being adsorbed to the entire surface of the recess, and/orstep (b-2) of step (b) suppresses the first reactant and the secondreactant from reacting on the entire surface of the recess. That is, thesubstrate processing method according to the embodiment may beterminated before the adsorption of the first reactant to the entiresurface in the depth direction of the pattern is completed. Accordingly,by adjusting the processing conditions in step (b-1), the position wherethe protective film is to be formed may be adjusted. In addition, in theembodiment, step (b-2) may be ended before the reaction of the secondreactant on the entire surface in the depth direction of the pattern iscompleted. Accordingly, by adjusting the processing conditions in step(b-2), the position where the protective film is to be formed may beadjusted. For example, the decrease of the etching rate may besuppressed by suppressing the protective layer from being formed on thebottom.

Further, the substrate processing method according to the embodiment mayfurther include step (c) of etching the bottom of the recess to form arecess with a high aspect ratio, after step (b). As a result, accordingto the embodiment, the pattern is further processed after the protectivefilm is formed, so that a desired shape of the pattern may beimplemented.

Further, in the substrate processing method according to the embodiment,step (b) may be further performed after step (c). As a result, accordingto the embodiment, even when the protective film is lost due to theetching, the protective film is formed again so that a desired patternmay be formed.

Further, in the substrate processing method according to the embodiment,the workpiece may include a substrate, an etching target film formed onthe substrate, and a mask formed on the etching target film. Inaddition, the substrate processing method may further include step (d)of forming a preliminary film on the top of the mask to reduce theopening dimension of the recess. As a result, in the substrateprocessing method according to the embodiment, for example, thepreliminary film is formed on the top of the pattern formed on theworkpiece by the chemical vapor deposition or the physical vapordeposition, so that the opening dimension at the top of the recess maybe reduced. As a result, the substrate processing method according tothe embodiment increases the aspect ratio of the recess. Thus, accordingto the embodiment, the film formation may be implemented using thesub-conformal ALD for a recess with a low aspect ratio as well.

Further, in the substrate processing method according to the embodiment,step (d) may be performed before step (b). As a result, according to theembodiment, the sub-conformal ALD may be performed after the aspectratio of the recess is corrected.

Further, in the substrate processing method according to the embodiment,step (d) may be performed when the aspect ratio of the recess is lessthan 10. Further, in the substrate processing method according to theembodiment, step (d) may be performed when the ratio of the depthdimension from the upper surface of the mask to the bottom of the recessto the opening dimension at the top of the recess is less than 15. Inaddition, in the substrate processing method according to theembodiment, steps (a) and (b) may be repeated when the aspect ratio ofthe recess is 10 or more, or when the ratio of the depth dimension fromthe upper surface of the mask to the bottom of the recess to the openingdimension at the top of the recess is 15 or more. As a result, accordingto the embodiment, when the aspect ratio of the recess becomes low, theprocessing of stopping the sub-conformal ALD and increasing the aspectratio may be performed. Further, the sub-conformal ALD may beeffectively performed while the aspect ratio of the recess is high. Inthis way, according to the embodiment, the aspect ratio of the recessmay be adjusted to a value suitable for the control of film formation,and then, the film formation may be performed.

Further, in the substrate processing method according to the embodiment,the processing conditions of at least one of steps (b-1) and (b-2) maybe changed according to the aspect ratio of the recess, after step (a)or (c). As a result, according to the embodiment, the processing of thepattern may be continued by forming the protective film suitable for thestate of the pattern after the etching.

Further, in the substrate processing method according to the embodiment,when step (b) is repeated at least “n” or more times (“n” is a naturalnumber of 2 or more), the processing conditions may be changed in ann-th processing and an (n-1)-th processing. Accordingly, the positionand/or the thickness of the film in repeated step (b) may be changed. Asa result, according to the embodiment, the shape and/or the position ofthe film to be formed may be further finely adjusted.

Further, in the substrate processing method according to the embodiment,when step (b) is repeated at least n′ or more times (n′ is a naturalnumber of 2 or more), the first reactant and the second reactant used inan n-th processing and an (n-1)-th processing may be changed.Accordingly, the position and/or the thickness of the film formed inrepeated step (b) may be changed. As a result, according to theembodiment, the shape and/or the position of the film to be formed maybe further finely adjusted.

Further, the substrate processing method according to the embodiment mayinclude steps (a), (b), and (e). Step (a) forms a recess on a workpiecedisposed on the stage in the processing chamber by etching theworkpiece. Step (b) forms a film having a thickness that differs alongthe depth direction of the recess, on the side wall of the recess. Step(e) etches the workpiece while suppressing the change of the openingdimension in the upper portion of the recess by the film formed in step(b), and expands the opening dimension of the lower portion of therecess that is not covered with the film formed in step (b) in thehorizontal direction.

Further, in the substrate processing method according to the embodiment,step (e) may further expand the opening dimension of the lower portionof the recess that is not covered with the film in the verticaldirection, in addition to the horizontal direction. In addition, when astep of forming a recess with a high aspect ratio by etching the bottomof the recess is included after step (b), step (c) may etch the bottomof the recess by an anisotropic etching, and step (e) may expand theopening dimension of the lower portion of the recess in the horizontaldirection by an isotropic etching.

Further, in the substrate processing method according to the embodiment,in step (b), each of the plurality of zones provided on the stage onwhich the workpiece is to be disposed and configured such that thetemperatures of the plurality of zones are independently controllablemay be controlled to have a different temperature according to anin-plane position of each of the plurality of zones. As a result, thethickness of the film to be formed may be changed according to thetemperatures of the plurality of zones. Thus, according to theembodiment, the state of film formation may be adjusted by controllingthe temperature of the stage.

Further, in the substrate processing method according to the embodiment,steps (a), (b), and (c) may be repeated at least n″ times (n″ is anatural number of 2 or more). Then, in step (b-2) of an (n″-1)-thprocessing, each of the plurality of zones provided on the stage onwhich the workpiece is to be disposed and configured such that thetemperatures of the plurality of zones are independently controllablemay be controlled to be a first temperature distribution. Then, a firstfilm having a first thickness distribution in the depth direction may beformed. In addition, in step (b-2) of an n″-th processing, each of theplurality of zones may be controlled to be a second temperaturedistribution. Then, a second film having a second thickness distributionin the depth direction may be formed. As a result, according to theembodiment, the state of film formation may be adjusted by controllingthe temperature of the stage.

Further, in the substrate processing method according to the embodiment,the pressure of the processing chamber in step (b-1) may be set to asmaller value than that of a pressure at which the adsorption of thefirst reactant to the entire surface of the recess in the depthdirection of the recess is completed, when the other processingconditions are the same. In addition, the processing time in step (b-1)may be set to be shorter than a processing time for which the adsorptionof the first reactant to the entire surface of the recess in the depthdirection of the recess is completed, when the other processingconditions are the same. In addition, the dilution degree of the firstreactant in step (b-1) may be set to a higher value than that of adilution degree at which the adsorption of the first reactant to theentire surface of the recess in the depth direction of the recess iscompleted, when the other processing conditions are the same. Inaddition, the temperature of the stage of the workpiece in step (b-1)may be set to be lower than a temperature at which the adsorption of thefirst reactant to the entire surface of the recess in the depthdirection of the recess is completed, when the other processingconditions are the same. In addition, when plasma is generated in step(b-1), the absolute value of the radio-frequency (RF) power applied forgenerating plasma may be set to be smaller than an absolute value atwhich the reaction of the second reactant on the entire surface of therecess in the depth direction of the recess is completed, when the otherprocessing conditions are the same. In this way, the adsorption of thecomponent contained in the first reactant to the workpiece may beimplemented, while changing the coverage along the depth direction ofthe recess by adjusting the processing conditions in step (b-1).

Further, in the substrate processing method according to the embodiment,the pressure of the processing chamber in step (b-2) may be set to asmaller value than that of a pressure at which the reaction of thesecond reactant on the entire surface of the recess in the depthdirection of the recess is completed, when the other processingconditions are the same. In addition, the processing time in step (b-2)may be set to be shorter than a processing time for which the reactionof the second reactant on the entire surface of the recess in the depthdirection of the recess is completed, when the other processingconditions are the same. In addition, the dilution degree of the secondreactant in step (b-2) may be set to a higher value than that of adilution degree at which the reaction of the second reactant on theentire surface of the recess in the depth direction of the recess iscompleted, when the other processing conditions are the same. Inaddition, the temperature of the stage of the workpiece in step (b-2)may be set to be lower than a temperature at which the reaction of thesecond reactant on the entire surface of the recess in the depthdirection of the recess is completed, when the other processingconditions are the same. In addition, when plasma is generated in step(b-2), the absolute value of the radio-frequency (RF) power applied forgenerating plasma may be set to be smaller than an absolute value atwhich the reaction of the second reactant on the entire surface of therecess in the depth direction of the recess is completed, when the otherprocessing conditions are the same. In this way, the reaction of thecomponent contained in the second reactant on the surface of theworkpiece may be implemented, while changing the coverage along thedepth direction of the recess by adjusting the processing conditions instep (b-2).

Further, the substrate processing method according to the embodimentdescribed above may further include, step (f) of forming an inhibitorthat inhibits the adsorption of the first reactant on the side wall ofthe recess, before step (b-1). As a result, according to the embodiment,the protective film may be formed at an arbitrary position.

Further, the substrate processing method according to the embodimentdescribed above may further include step (g) of performing a coating forcovering by-product adhering to the inner wall of the processingchamber, after step (a). As a result, according to the embodiment, thechange of the condition and state in the processing chamber may beprevented. Thus, according to the embodiment, the state of the film tobe formed may be stabilized.

Further, in the substrate processing apparatus according to theembodiment, step (b) may include steps (b-3), (b-4), and (b-5). Step(b-3) measures a parameter that indicates a state of a formed film. Step(b-4) determines whether the film is in a preset state, based on themeasured value. Step (b-5) adjusts the processing conditions based onthe measured value, and then, repeats steps (b-1) and (b-2), when it isdetermined that the film is not in the preset state.

In addition, the substrate processing apparatus according to theembodiment includes one or more processing chambers of which at leastone processing chamber is configured to perform an etching and at leastone processing chamber is configured to form a film, and a controller.Each processing chamber includes a gas supply that supplies a processinggas into the processing chamber. The controller causes each unit of thesubstrate processing apparatus to perform the substrate processingmethod. The substrate processing method includes steps (a) and (b). Step(a) forms a recess on a workpiece by partially etching the workpiece.Step (b) forms a film having a thickness that differs along a depthdirection of the recess, on the side wall of the recess. Step (b)includes steps (b-1) and (b-2). Step (b-1) supplies the first reactantinto the processing chamber configured to form a film, and causes thefirst reactant to be adsorbed to the side wall of the recess. Step (b-2)supplies the second reactant into the processing chamber configured toform a film, and causes the second reactant to react with the firstreactant thereby forming a film. Thus, according to the embodiment, thefilm thickness of the film to be formed on the pattern with the highaspect ratio may be changed along the depth direction. As a result,according to the embodiment, it is possible to form the protective filmin advance at the position of the pattern where the shape abnormalitymay easily occur, while changing the film thickness in the depthdirection. Thus, according to the embodiment, the shape abnormality of asemiconductor pattern may be suppressed. In addition, according to theembodiment, since the film having the self-controllability, for example,the ALD film is formed, the film thickness of the protective film to beformed may be precisely controlled. As a result, according to theembodiment, the closing of the opening of the pattern may be suppressed.In addition, according to the embodiment, by suppressing the protectivefilm from being formed on the bottom of the pattern, the etching stop isprevented so that the etching rate may be improved. Further, accordingto the embodiment, the coverage of the protective film along the depthdirection of the pattern may be largely changed by adjusting theprocessing conditions of steps (b-1) and (b-2).

In addition, in the substrate processing apparatus according to theembodiment, the processing chamber configured to perform an etching maybe the same as the processing chamber configured to form a film, andsteps (a) and (b) may be performed in the same processing chamber.

In addition, in the substrate processing apparatus according to theembodiment, the processing chamber configured to perform an etching maybe different from the processing chamber configured to form a film.Then, the controller may cause each unit of the substrate processingapparatus to perform the substrate processing method that furtherincludes (h) transferring the substrate between the processing chamberconfigured to perform an etching and the processing chamber configuredto form a film.

According to the present disclosure, it is possible to suppress theshape abnormality of a semiconductor pattern.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A method of processing a substrate comprising:(a) forming a recess on a substrate by partially etching the substrate;and (b) forming a film having a thickness that differs along a depthdirection of the recess, on a side wall of the recess, wherein (b)includes: (b-1) supplying a first reactant, and allowing the firstreactant to adsorb onto the side wall of the recess; and (b-2) supplyinga second reactant, wherein the first and second reactants react witheach other to form the film.
 2. The method of claim 1, wherein in (b),(b-1) suppresses the first reactant from adsorbing onto an entiresurface of the recess, and/or (b-2) suppresses the first reactant andthe second reactant from reacting on the entire surface of the recess.3. The method of claim 2, further comprising: (c) etching a bottom ofthe recess to form a recess with a high aspect ratio, after (b).
 4. Themethod of claim 3, wherein (b) is further performed after (c).
 5. Themethod of claim 4, wherein the substrate includes an etching target filmand a mask formed on the etching target film, and the method furthercomprises: (d) forming a preliminary film on a top of the mask to reducean opening dimension of the recess.
 6. The method of claim 5, wherein(d) is performed prior to (b).
 7. The method of claim 5, wherein (d) isperformed when the aspect ratio of the recess is less than
 10. 8. Themethod of claim 5, wherein (d) is performed when a ratio of a depthdimension from an upper surface of the mask to the bottom of the recesswith respect to the opening dimension of the recess at a top of therecess is less than
 15. 9. The method of claim 5, wherein (a) and (b)are repeated when the aspect ratio of the recess is 10 or more, or whenthe ratio of the depth dimension from the upper surface of the mask tothe bottom of the recess with respect to the opening dimension of therecess at the top of the recess is 15 or more.
 10. The method of claim3, wherein after (a) or (c), processing conditions of at least one of(b-1) and (b-2) are changed according to the aspect ratio of the recess.11. The method of claim 1, wherein when (b) is repeated n or more times(n is a natural number of 2 or more), a position and/or a thickness ofthe film formed in repeated (b) are changed by changing processingconditions in an n-th processing and an (n-1)-th processing.
 12. Themethod of claim 11, wherein when (b) is repeated n′ or more times (n′ isa natural number of 2 or more), a position and/or a thickness of thefilm formed in repeated (b) are changed by changing the first reactantand the second reactant used in an n′-th processing and an (n′-1)-thprocessing.
 13. The method of claim 1, wherein in (b), the substrate isdisposed on a stage provided with a plurality of zones and configuredsuch that temperatures of the plurality of zones are independentlycontrollable, and each of the plurality of zones is controlled to have adifferent temperature according to an in-plane position of thecorresponding zone, thereby changing the thickness of the film to beformed according to the temperatures of the plurality of zones.
 14. Themethod of claim 1, wherein the substrate is disposed on a stage providedwith a plurality of zones and configured such that temperatures of theplurality of zones are independently controllable, (a) and (b) arerepeated at least n″ times (n″ is a natural number of 2 or more), in(b-2) of an (n″-1)-th processing, each of the plurality of zones iscontrolled to be a first temperature distribution, thereby forming afirst film having a first film thickness distribution in a depthdirection, and in (b-2) of an n″-th processing, each of the plurality ofzones is controlled to be a second temperature distribution, therebyforming a second film having a second film thickness distribution in thedepth direction.
 15. The method of claim 1, wherein the processingconditions in (b-1) satisfy at least one of following conditions (1) to(5): (1) when other processing conditions are same, a pressure of aprocessing chamber is set to a smaller value than that of a pressure atwhich an adsorption of the first reactant to an entire surface of therecess in a depth direction of the recess is completed, (2) when otherprocessing conditions are same, a processing time is set to be shorterthan a processing time for which the adsorption of the first reactant tothe entire surface of the recess in the depth direction of the recess iscompleted, (3) when other processing conditions are same, a dilutiondegree of the first reactant is set to a higher value than that of adilution degree at which the adsorption of the first reactant to theentire surface of the recess in the depth direction of the recess iscompleted, (4) when other processing conditions are same, a temperatureof a stage disposed the substrate is set to be lower than a temperatureat which the adsorption of the first reactant to the entire surface ofthe recess in the depth direction of the recess is completed, and (5)when other processing conditions are same and when plasma is generatedin (b-1), an absolute value of a radio-frequency (RF) power applied forgenerating plasma is set to be smaller than an absolute value at whichthe adsorption of the first reactant to the entire surface of the recessin the depth direction of the recess is completed.
 16. The method ofclaim 1, wherein the processing conditions in (b-2) satisfy at least oneof following conditions (1) to (5): (1) when other processing conditionsare same, a pressure of the processing chamber is set to a smaller valuethan that of a pressure at which a reaction of the second reactant on anentire surface of the recess in a depth direction of the recess iscompleted, (2) when other processing conditions are same, a processingtime is set to be shorter than a processing time for which the reactionof the second reactant on the entire surface of the recess in the depthdirection of the recess is completed, (3) when other processingconditions are same, a dilution degree of the second reactant is set toa higher value than that of a dilution degree at which the reaction ofthe second reactant on the entire surface of the recess in the depthdirection of the recess is completed, (4) when other processingconditions are same, a temperature of a stage disposed the substrate isset to be lower than a temperature at which the reaction of the secondreactant to the entire surface of the recess in the depth direction ofthe recess is completed, and (5) when other processing conditions aresame and when plasma is generated in (b-1), an absolute value of aradio-frequency (RF) power applied for generating plasma is set to besmaller than an absolute value at which the reaction of the secondreactant on the entire surface of the recess in the depth direction ofthe recess is completed.
 17. The method of claim 1, further comprising:(e) forming an inhibitor that inhibits the adsorption of the firstreactant, on the side wall of the recess before (b-1).
 18. The method ofclaim 1, further comprising: (g) performing a coating process forcovering by-products adhering to an inner wall of a processing chamber,after (a).